Science

Spatially ordered dynamics of the bacterial carbon fixation machinery.

Publication Date: 2010 Mar 5 PMID: 20203050
Authors: Savage, D. F. - Afonso, B. - Chen, A. H. - Silver, P. A.
Journal: Science

Cyanobacterial carbon fixation is a major component of the global carbon cycle. This process requires the carboxysome, an organelle-like proteinaceous microcompartment that sequesters the enzymes of carbon fixation from the cytoplasm. Here, fluorescently tagged carboxysomes were found to be spatially ordered in a linear fashion. As a consequence, cells undergoing division evenly segregated carboxysomes in a nonrandom process. Mutation of the cytoskeletal protein ParA specifically disrupted carboxysome order, promoted random carboxysome segregation during cell division, and impaired carbon fixation after disparate partitioning. Thus, cyanobacteria use the cytoskeleton to control the spatial arrangement of carboxysomes and to optimize the metabolic process of carbon fixation.

post to: CiteULike

RTEL-1 enforces meiotic crossover interference and homeostasis.

Publication Date: 2010 Mar 5 PMID: 20203049
Authors: Youds, J. L. - Mets, D. G. - McIlwraith, M. J. - Martin, J. S. - Ward, J. D. - ONeil, N. J. - Rose, A. M. - West, S. C. - Meyer, B. J. - Boulton, S. J.
Journal: Science

Meiotic crossovers (COs) are tightly regulated to ensure that COs on the same chromosome are distributed far apart (crossover interference, COI) and that at least one CO is formed per homolog pair (CO homeostasis). CO formation is controlled in part during meiotic double-strand break (DSB) creation in Caenorhabditis elegans, but a second level of control must also exist because meiotic DSBs outnumber COs. We show that the antirecombinase RTEL-1 is required to prevent excess meiotic COs, probably by promoting meiotic synthesis-dependent strand annealing. Two distinct classes of meiotic COs are increased in rtel-1 mutants, and COI and homeostasis are compromised. We propose that RTEL-1 implements the second level of CO control by promoting noncrossovers.

post to: CiteULike

Hippocampal short- and long-term plasticity are not modulated by astrocyte Ca2+ signaling.

Publication Date: 2010 Mar 5 PMID: 20203048
Authors: Agulhon, C. - Fiacco, T. A. - McCarthy, K. D.
Journal: Science

The concept that astrocytes release neuroactive molecules (gliotransmitters) to affect synaptic transmission has been a paradigm shift in neuroscience research over the past decade. This concept suggests that astrocytes, together with pre- and postsynaptic neuronal elements, make up a functional synapse. Astrocyte release of gliotransmitters (for example, glutamate and adenosine triphosphate) is generally accepted to be a Ca2+-dependent process. We used two mouse lines to either selectively increase or obliterate astrocytic Gq G protein-coupled receptor Ca2+ signaling to further test the hypothesis that astrocytes release gliotransmitters in a Ca2+-dependent manner to affect synaptic transmission. Neither increasing nor obliterating astrocytic Ca2+ fluxes affects spontaneous and evoked excitatory synaptic transmission or synaptic plasticity. Our findings suggest that, at least in the hippocampus, the mechanisms of gliotransmission need to be reconsidered.

post to: CiteULike

Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf.

Publication Date: 2010 Mar 5 PMID: 20203047
Authors: Shakhova, N. - Semiletov, I. - Salyuk, A. - Yusupov, V. - Kosmach, D. - Gustafsson, O.
Journal: Science

Remobilization to the atmosphere of only a small fraction of the methane held in East Siberian Arctic Shelf (ESAS) sediments could trigger abrupt climate warming, yet it is believed that sub-sea permafrost acts as a lid to keep this shallow methane reservoir in place. Here, we show that more than 5000 at-sea observations of dissolved methane demonstrates that greater than 80% of ESAS bottom waters and greater than 50% of surface waters are supersaturated with methane regarding to the atmosphere. The current atmospheric venting flux, which is composed of a diffusive component and a gradual ebullition component, is on par with previous estimates of methane venting from the entire World Ocean. Leakage of methane through shallow ESAS waters needs to be considered in interactions between the biogeosphere and a warming Arctic climate.

post to: CiteULike

The role of sulfuric acid in atmospheric nucleation.

Publication Date: 2010 Mar 5 PMID: 20203046
Authors: Sipila, M. - Berndt, T. - Petaja, T. - Brus, D. - Vanhanen, J. - Stratmann, F. - Patokoski, J. - Mauldin, R. L. 3rd - Hyvarinen, A. P. - Lihavainen, H. - Kulmala, M.
Journal: Science

Nucleation is a fundamental step in atmospheric new-particle formation. However, laboratory experiments on nucleation have systematically failed to demonstrate sulfuric acid particle formation rates as high as those necessary to account for ambient atmospheric concentrations, and the role of sulfuric acid in atmospheric nucleation has remained a mystery. Here, we report measurements of new particles (with diameters of approximately 1.5 nanometers) observed immediately after their formation at atmospherically relevant sulfuric acid concentrations. Furthermore, we show that correlations between measured nucleation rates and sulfuric acid concentrations suggest that freshly formed particles contain one to two sulfuric acid molecules, a number consistent with assumptions that are based on atmospheric observations. Incorporation of these findings into global models should improve the understanding of the impact of secondary particle formation on climate.

post to: CiteULike

Calibrating the Cryogenian.

Publication Date: 2010 Mar 5 PMID: 20203045
Authors: Macdonald, F. A. - Schmitz, M. D. - Crowley, J. L. - Roots, C. F. - Jones, D. S. - Maloof, A. C. - Strauss, J. V. - Cohen, P. A. - Johnston, D. T. - Schrag, D. P.
Journal: Science

The Neoproterozoic was an era of great environmental and biological change, but a paucity of direct and precise age constraints on strata from this time has prevented the complete integration of these records. We present four high-precision U-Pb ages for Neoproterozoic rocks in northwestern Canada that constrain large perturbations in the carbon cycle, a major diversification and depletion in the microfossil record, and the onset of the Sturtian glaciation. A volcanic tuff interbedded with Sturtian glacial deposits, dated at 716.5 million years ago, is synchronous with the age of the Franklin large igneous province and paleomagnetic poles that pin Laurentia to an equatorial position. Ice was therefore grounded below sea level at very low paleolatitudes, which implies that the Sturtian glaciation was global in extent.

post to: CiteULike

Geodynamo, solar wind, and magnetopause 3.4 to 3.45 billion years ago.

Publication Date: 2010 Mar 5 PMID: 20203044
Authors: Tarduno, J. A. - Cottrell, R. D. - Watkeys, M. K. - Hofmann, A. - Doubrovine, P. V. - Mamajek, E. E. - Liu, D. - Sibeck, D. G. - Neukirch, L. P. - Usui, Y.
Journal: Science

Stellar wind standoff by a planetary magnetic field prevents atmospheric erosion and water loss. Although the early Earth retained its water and atmosphere, and thus evolved as a habitable planet, little is known about Earth's magnetic field strength during that time. We report paleointensity results from single silicate crystals bearing magnetic inclusions that record a geodynamo 3.4 to 3.45 billion years ago. The measured field strength is approximately 50 to 70% that of the present-day field. When combined with a greater Paleoarchean solar wind pressure, the paleofield strength data suggest steady-state magnetopause standoff distances of < or = 5 Earth radii, similar to values observed during recent coronal mass ejection events. The data also suggest lower-latitude aurora and increases in polar cap area, as well as heating, expansion, and volatile loss from the exosphere that would have affected long-term atmospheric composition.

post to: CiteULike

Sestrin as a feedback inhibitor of TOR that prevents age-related pathologies.

Publication Date: 2010 Mar 5 PMID: 20203043
Authors: Lee, J. H. - Budanov, A. V. - Park, E. J. - Birse, R. - Kim, T. E. - Perkins, G. A. - Ocorr, K. - Ellisman, M. H. - Bodmer, R. - Bier, E. - Karin, M.
Journal: Science

Sestrins are conserved proteins that accumulate in cells exposed to stress, potentiate adenosine monophosphate-activated protein kinase (AMPK), and inhibit activation of target of rapamycin (TOR). We show that the abundance of Drosophila sestrin (dSesn) is increased upon chronic TOR activation through accumulation of reactive oxygen species that cause activation of c-Jun amino-terminal kinase and transcription factor Forkhead box O (FoxO). Loss of dSesn resulted in age-associated pathologies including triglyceride accumulation, mitochondrial dysfunction, muscle degeneration, and cardiac malfunction, which were prevented by pharmacological activation of AMPK or inhibition of TOR. Hence, dSesn appears to be a negative feedback regulator of TOR that integrates metabolic and stress inputs and prevents pathologies caused by chronic TOR activation that may result from diminished autophagic clearance of damaged mitochondria, protein aggregates, or lipids.

post to: CiteULike

The Chicxulub asteroid impact and mass extinction at the Cretaceous-Paleogene boundary.

Publication Date: 2010 Mar 5 PMID: 20203042
Authors: Schulte, P. - Alegret, L. - Arenillas, I. - Arz, J. A. - Barton, P. J. - Bown, P. R. - Bralower, T. J. - Christeson, G. L. - Claeys, P. - Cockell, C. S. - Collins, G. S. - Deutsch, A. - Goldin, T. J. - Goto, K. - Grajales-Nishimura, J. M. - Grieve, R. A. - Gulick, S. P. - Johnson, K. R. - Kiessling, W. - Koeberl, C. - Kring, D. A. - MacLeod, K. G. - Matsui, T. - Melosh, J. - Montanari, A. - Morgan, J. V. - Neal, C. R. - Nichols, D. J. - Norris, R. D. - Pierazzo, E. - Ravizza, G. - Rebolledo-Vieyra, M. - Reimold, W. U. - Robin, E. - Salge, T. - Speijer, R. P. - Sweet, A. R. - Urrutia-Fucugauchi, J. - Vajda, V. - Whalen, M. T. - Willumsen, P. S.
Journal: Science

The Cretaceous-Paleogene boundary approximately 65.5 million years ago marks one of the three largest mass extinctions in the past 500 million years. The extinction event coincided with a large asteroid impact at Chicxulub, Mexico, and occurred within the time of Deccan flood basalt volcanism in India. Here, we synthesize records of the global stratigraphy across this boundary to assess the proposed causes of the mass extinction. Notably, a single ejecta-rich deposit compositionally linked to the Chicxulub impact is globally distributed at the Cretaceous-Paleogene boundary. The temporal match between the ejecta layer and the onset of the extinctions and the agreement of ecological patterns in the fossil record with modeled environmental perturbations (for example, darkness and cooling) lead us to conclude that the Chicxulub impact triggered the mass extinction.

post to: CiteULike

Neuroscience. Questionable calcium.

Publication Date: 2010 Mar 5 PMID: 20203041
Authors: Kirchhoff, F.
Journal: Science

post to: CiteULike

Climate change. How stable is the methane cycle?

Publication Date: 2010 Mar 5 PMID: 20203040
Authors: Heimann, M.
Journal: Science

post to: CiteULike

Cell biology. Burn out or fade away?

Publication Date: 2010 Mar 5 PMID: 20203039
Authors: Topisirovic, I. - Sonenberg, N.
Journal: Science

post to: CiteULike

Physics. Controlling implosion symmetry around a deuterium-tritium target.

Publication Date: 2010 Mar 5 PMID: 20203038
Authors: Norreys, P. A.
Journal: Science

post to: CiteULike

Ecology. The Seven Ages of Pan.

Publication Date: 2010 Mar 5 PMID: 20203037
Authors: Clutton-Brock, T. - Sheldon, B. C.
Journal: Science

post to: CiteULike

Astronomy. Sunscreen for the young Earth.

Publication Date: 2010 Mar 5 PMID: 20203036
Authors: Jardine, M.
Journal: Science

post to: CiteULike

Energy. Behavior and energy policy.

Publication Date: 2010 Mar 5 PMID: 20203035
Authors: Allcott, H. - Mullainathan, S.
Journal: Science

post to: CiteULike

Comment on "Movement intention after parietal cortex stimulation in humans".

Publication Date: 2010 Mar 5 PMID: 20203033
Authors: Karnath, H. O. - Borchers, S. - Himmelbach, M.
Journal: Science

Desmurget et al. (Reports, 8 May 2009, p. 811) applied direct electrical stimulation (DES) to the human cortex to study the origin of movement intention. Their interpretation assumed that DES causes cortical activation, whereas it is possible that it actually evokes deactivation. The lack of certain knowledge about the true effects of DES limits its use for validation of cognitive models.

post to: CiteULike

A greener future for China's cities.

Publication Date: 2010 Mar 5 PMID: 20203032
Authors: Wang, Z. - Chen, J. M.
Journal: Science

post to: CiteULike

Bioenergy: counting on incentives.

Publication Date: 2010 Mar 5 PMID: 20203031
Authors: Pingoud, K. - Cowie, A. - Bird, N. - Gustavsson, L. - Ruter, S. - Sathre, R. - Soimakallio, S. - Turk, A. - Woess-Gallasch, S.
Journal: Science

post to: CiteULike

17th Conference on Retroviruses and Opportunistic Infections, 16-19 February, San Francisco, CA. Limits of success.

Publication Date: 2010 Mar 5 PMID: 20203030
Authors: Cohen, J.
Journal: Science

post to: CiteULike

17th Conference on Retroviruses and Opportunistic Infections, 16-19 February, San Francisco, CA. The ins and outs of HIV.

Publication Date: 2010 Mar 5 PMID: 20203029
Authors: Cohen, J.
Journal: Science

post to: CiteULike

17th Conference on Retroviruses and Opportunistic Infections, 16-19 February, San Francisco, CA. Treatment as prevention.

Publication Date: 2010 Mar 5 PMID: 20203028
Authors: Cohen, J.
Journal: Science

post to: CiteULike

Astronomy. Unwinding the Milky Way.

Publication Date: 2010 Mar 5 PMID: 20203027
Authors: Bhattacharjee, Y.
Journal: Science

post to: CiteULike

Psychiatry. Anything but child's play.

Publication Date: 2010 Mar 5 PMID: 20203026
Authors: Miller, G.
Journal: Science

post to: CiteULike

Stem cells. Reprogrammed cells come up short, for now.

Publication Date: 2010 Mar 5 PMID: 20203025
Authors: Vogel, G.
Journal: Science

post to: CiteULike

Genomics. Semiconductors inspire new sequencing technologies.

Publication Date: 2010 Mar 5 PMID: 20203024
Authors: Pennisi, E.
Journal: Science

post to: CiteULike

Nutrition science. European food watchdog slashes dubious health claims.

Publication Date: 2010 Mar 5 PMID: 20203023
Authors: Enserink, M.
Journal: Science

post to: CiteULike

Archaeology. Of two minds about Toba's impact.

Publication Date: 2010 Mar 5 PMID: 20203021
Authors: Balter, M.
Journal: Science

post to: CiteULike

Paleoclimatology. Snowball Earth has melted back to a profound wintry mix.

Publication Date: 2010 Mar 5 PMID: 20203019
Authors: Kerr, R. A.
Journal: Science

post to: CiteULike

Pharmacology. Growth hormone test finally nabs first doper.

Publication Date: 2010 Mar 5 PMID: 20203018
Authors: Travis, J.
Journal: Science

post to: CiteULike

Seismology. Two years later, new rumblings over origins of Sichuan quake.

Publication Date: 2010 Mar 5 PMID: 20203017
Authors: Kerr, R. A. - Stone, R.
Journal: Science

post to: CiteULike

Biodiversity is our life.

Publication Date: 2010 Mar 5 PMID: 20203016
Authors: Marton-Lefevre, J.
Journal: Science

post to: CiteULike

Solvent-Mediated Electron Hopping: Long-Range Charge Transfer In IBr-(CO2) Photodissociation.

Publication Date: 2010 Mar 4 PMID: 20203015
Authors: Sheps, L. - Miller, E. M. - Horvath, S. - Thompson, M. A. - Parson, R. - McCoy, A. B. - Lineberger, W. C.
Journal: Science

Chemical bond breaking involves coupled electronic and nuclear dynamics that can take place on multiple electronic surfaces. Here, we report a time-resolved experimental and theoretical investigation of nonadiabatic dynamics during photodissociation of IBr(-)(CO(2)) excited to the A' electronic state. Previous experimental work showed that dissociation of bare IBr(-) yields only I(-) + Br products. However, in IBr(-)(CO(2)), time-resolved photoelectron spectroscopy reveals that a subset of the dissociating molecules undergo an electron transfer from iodine to bromine 350 fs after the initial excitation. Ab initio calculations and molecular dynamics simulations elucidate the mechanism for this charge hop and highlight the crucial role of the CO(2) molecule. The charge transfer between two recoiling atoms, assisted by a single solvent-like molecule, provides a remarkable limiting case of solvent-driven electron transfer over a distance of 7 A.

post to: CiteULike

Iron-Clad Fibers: A Metal-Based Biological Strategy for Hard Flexible Coatings.

Publication Date: 2010 Mar 4 PMID: 20203014
Authors: Harrington, M. J. - Masic, A. - Holten-Andersen, N. - Waite, J. H. - Fratzl, P.
Journal: Science

The extensible byssal threads of marine mussels are shielded from abrasion in wave-swept habitats by an outer cuticle that is largely proteinaceous and ~5-fold harder than the thread core. Threads from several species exhibit granular cuticles containing a protein rich in the catecholic amino acid 3,4-dihydroxyphenylalanine (dopa), as well as inorganic ions, notably Fe(3+). Granular cuticles exhibit a remarkable combination of high hardness and high extensibility. We explore byssus cuticle chemistry by in situ resonance Raman spectroscopy and demonstrate that the cuticle is a polymeric scaffold stabilized by catecholato-iron chelate complexes having an unusual clustered distribution. Consistent with byssal cuticle chemistry and mechanics, we present a model where dense cross-linking in the granules provides hardness, whereas the less cross-linked matrix provides extensibility.

post to: CiteULike

Metabolic Syndrome and Altered Gut Microbiota in Mice Lacking Toll-Like Receptor 5.

Publication Date: 2010 Mar 4 PMID: 20203013
Authors: Vijay-Kumar, M. - Aitken, J. D. - Carvalho, F. A. - Cullender, T. C. - Mwangi, S. - Srinivasan, S. - Sitaraman, S. V. - Knight, R. - Ley, R. E. - Gewirtz, A. T.
Journal: Science

Metabolic syndrome is a group of obesity-related metabolic abnormalities that increase an individual's risk of developing type 2 diabetes and cardiovascular disease. Here, we show that mice genetically deficient in Toll-like receptor 5 (TLR5), a component of the innate immune system that is expressed in the gut mucosa and that helps defend against infection, exhibit hyperphagia and develop hallmark features of metabolic syndrome, including hyperlipidemia, hypertension, insulin resistance, and increased adiposity. These metabolic changes correlated with changes in the composition of the gut microbiota and, importantly, transfer of the gut microbiota from TLR5-deficient mice to wild-type germ-free mice conferred many features of metabolic syndrome to the recipients. Food restriction prevented obesity, but not insulin resistance, in the TLR5-deficient mice. These results support the emerging view that the gut microbiota contributes to metabolic disease and suggest that malfunction of the innate immune system may promote the development of metabolic syndrome.

post to: CiteULike

Cryptic Sex-Ratio Bias Provides Indirect Genetic Benefits Despite Sexual Conflict.

Publication Date: 2010 Mar 4 PMID: 20203012
Authors: Cox, R. M. - Calsbeek, R.
Journal: Science

When selection favors sexual dimorphism, high-fitness parents often produce low-fitness progeny of the opposite sex. This sexual conflict is thought to overwhelm the genetic benefits of mate choice because preferred males incur a cost through the production of low-fitness daughters. We provide a counterpoint in a lizard that exhibits sexual conflict over body size. Using mate-choice experiments, we show that female brown anoles (Anolis sagrei) produce more sons than daughters via large sires, but more daughters than sons via small sires. Measures of progeny fitness in the wild suggest that maximal fitness payoffs can be achieved by shifting offspring production from daughters to sons as sire size increases. These results illustrate how the resolution of sexual conflict can restore the genetic benefits of mate choice.

post to: CiteULike

Observation of an Antimatter Hypernucleus.

Publication Date: 2010 Mar 4 PMID: 20203011
Authors: Abelev, B. I. - Aggarwal, M. M. - Ahammed, Z. - Alakhverdyants, A. V. - Alekseev, I. - Anderson, B. D. - Arkhipkin, D. - Averichev, G. S. - Balewski, J. - Barnby, L. S. - Baumgart, S. - Beavis, D. R. - Bellwied, R. - Betancourt, M. J. - Betts, R. R. - Bhasin, A. - Bhati, A. K. - Bichsel, H. - Bielcik, J. - Bielcikova, J. - Biritz, B. - Bland, L. C. - Bonner, B. E. - Bouchet, J. - Braidot, E. - Brandin, A. V. - Bridgeman, A. - Bruna, E. - Bueltmann, S. - Bunzarov, I. - Burton, T. P. - Cai, X. Z. - Caines, H. - Calderon, M. - Catu, O. - Cebra, D. - Cendejas, R. - Cervantes, M. C. - Chajecki, Z. - Chaloupka, P. - Chattopadhyay, S. - Chen, H. F. - Chen, J. H. - Chen, J. Y. - Cheng, J. - Cherney, M. - Chikanian, A. - Choi, K. E. - Christie, W. - Chung, P. - Clarke, R. F. - Codrington, M. J. - Corliss, R. - Cramer, J. G. - Crawford, H. J. - Das, D. - Dash, S. - Leyva, A. D. - De Silva, L. C. - Debbe, R. R. - Dedovich, T. G. - Dephillips, M. - Derevschikov, A. A. - Derradi de Souza, R. - Didenko, L. - Djawotho, P. - Dogra, S. M. - Dong, X. - Drachenberg, J. L. - Draper, J. E. - Dunlop, J. C. - Mazumdar, M. R. - Efimov, L. G. - Elhalhuli, E. - Elnimr, M. - Engelage, J. - Eppley, G. - Erazmus, B. - Estienne, M. - Eun, L. - Evdokimov, O. - Fachini, P. - Fatemi, R. - Fedorisin, J. - Fersch, R. G. - Filip, P. - Finch, E. - Fine, V. - Fisyak, Y. - Gagliardi, C. A. - Gangadharan, D. R. - Ganti, M. S. - Garcia-Solis, E. J. - Geromitsos, A. - Geurts, F. - Ghazikhanian, V. - Ghosh, P. - Gorbunov, Y. N. - Gordon, A. - Grebenyuk, O. - Grosnick, D. - Grube, B. - Guertin, S. M. - Gupta, A. - Gupta, N. - Guryn, W. - Haag, B. - Hamed, A. - Han, L. X. - Harris, J. W. - Hays-Wehle, J. P. - Heinz, M. - Heppelmann, S. - Hirsch, A. - Hjort, E. - Hoffman, A. M. - Hoffmann, G. W. - Hofman, D. J. - Hollis, R. S. - Huang, B. - Huang, H. Z. - Humanic, T. J. - Huo, L. - Igo, G. - Iordanova, A. - Jacobs, P. - Jacobs, W. W. - Jakl, P. - Jena, C. - Jin, F. - Jones, C. L. - Jones, P. G. - Joseph, J. - Judd, E. G. - Kabana, S. - Kajimoto, K. - Kang, K. - Kapitan, J. - Kauder, K. - Keane, D. - Kechechyan, A. - Kettler, D. - Kikola, D. P. - Kiryluk, J. - Kisiel, A. - Klein, S. R. - Knospe, A. G. - Kocoloski, A. - Koetke, D. D. - Kollegger, T. - Konzer, J. - Kopytine, M. - Koralt, I. - Koroleva, L. - Korsch, W. - Kotchenda, L. - Kouchpil, V. - Kravtsov, P. - Krueger, K. - Krus, M. - Kumar, L. - Kurnadi, P. - Lamont, M. A. - Landgraf, J. M. - Lapointe, S. - Lauret, J. - Lebedev, A. - Lednicky, R. - Lee, C. H. - Lee, J. H. - Leight, W. - Levine, M. J. - Li, C. - Li, L. - Li, N. - Li, W. - Li, X. - Li, Y. - Li, Z. - Lin, G. - Lindenbaum, S. J. - Lisa, M. A. - Liu, F. - Liu, H. - Liu, J. - Ljubicic, T. - Llope, W. J. - Longacre, R. S. - Love, W. A. - Lu, Y. - Ludlam, T. - Luo, X. - Ma, G. L. - Ma, Y. G. - Mahapatra, D. P. - Majka, R. - Mal, O. I. - Mangotra, L. K. - Manweiler, R. - Margetis, S. - Markert, C. - Masui, H. - Matis, H. S. - Matulenko, Y. A. - McDonald, D. - McShane, T. S. - Meschanin, A. - Milner, R. - Minaev, N. G. - Mioduszewski, S. - Mischke, A. - Mitrovski, M. K. - Mohanty, B. - Mondal, M. M. - Morozov, B. - Morozov, D. A. - Munhoz, M. G. - Nandi, B. K. - Nattrass, C. - Nayak, T. K. - Nelson, J. M. - Netrakanti, P. K. - Ng, M. J. - Nogach, L. V. - Nurushev, S. B. - Odyniec, G. - Ogawa, A. - Okada, H. - Okorokov, V. - Olson, D. - Pachr, M. - Page, B. S. - Pal, S. K. - Pandit, Y. - Panebratsev, Y. - Pawlak, T. - Peitzmann, T. - Perevoztchikov, V. - Perkins, C. - Peryt, W. - Phatak, S. C. - Pile, P. - Planinic, M. - Ploskon, M. A. - Pluta, J. - Plyku, D. - Poljak, N. - Poskanzer, A. M. - Potukuchi, B. V. - Powell, C. B. - Prindle, D. - Pruneau, C. - Pruthi, N. K. - Pujahari, P. R. - Putschke, J. - Raniwala, R. - Raniwala, S. - Ray, R. L. - Redwine, R. - Reed, R. - Ritter, H. G. - Roberts, J. B. - Rogachevskiy, O. V. - Romero, J. L. - Rose, A. - Roy, C. - Ruan, L. - Sahoo, R. - Sakai, S. - Sakrejda, I. - Sakuma, T. - Salur, S. - Sandweiss, J. - Sangaline, E. - Schambach, J. - Scharenberg, R. P. - Schmitz, N. - Schuster, T. R. - Seele, J. - Seger, J. - Selyuzhenkov, I. - Seyboth, P. - Shahaliev, E. - Shao, M. - Sharma, M. - Shi, S. S. - Sichtermann, E. P. - Simon, F. - Singaraju, R. N. - Skoby, M. J. - Smirnov, N. - Sorensen, P. - Sowinski, J. - Spinka, H. M. - Srivastava, B. - Stanislaus, T. D. - Staszak, D. - Stevens, J. R. - Stock, R. - Strikhanov, M. - String, B. - Suaide, A. A. - Suarez, M. C. - Subba, N. L. - Sumbera, M. - Sun, X. M. - Sun, Y. - Sun, Z. - Surrow, B. - Svirida, D. N. - Symons, T. J. - Szanto de Toledo, A. - Takahashi, J. - Tang, A. H. - Tang, Z. - Tarini, L. H. - Tarnowsky, T. - Thein, D. - Thomas, J. H. - Tian, J. - Timmins, A. R. - Timoshenko, S. - Tlusty, D. - Tokarev, M. - Trainor, T. A. - Tram, V. N. - Trentalange, S. - Tribble, R. E. - Tsai, O. D. - Ulery, J. - Ullrich, T. - Underwood, D. G. - Van Buren, G. - van Leeuwen, M. - van Nieuwenhuizen, G. - Vanfossen, J. A. Jr - Varma, R. - Vasconcelos, G. M. - Vasiliev, A. N. - Videbaek, F. - Viyogi, Y. P. - Vokal, S. - Voloshin, S. A. - Wada, M. - Walker, M. - Wang, F. - Wang, G. - Wang, H. - Wang, J. S. - Wang, Q. - Wang, X. L. - Wang, Y. - Webb, G. - Webb, J. C. - Westfall, G. D. - Whitten, C. Jr - Wieman, H. - Wingfield, E. - Wissink, S. W. - Witt, R. - Wu, Y. - Xie, W. - Xu, N. - Xu, Q. H. - Xu, W. - Xu, Y. - Xu, Z. - Xue, L. - Yang, Y. - Yepes, P. - Yip, K. - Yoo, I. K. - Yue, Q. - Zawisza, M. - Zbroszczyk, H. - Zhan, W. - Zhang, J. - Zhang, S. - Zhang, W. M. - Zhang, X. P. - Zhang, Y. - Zhang, Z. P. - Zhao, J. - Zhong, C. - Zhou, J. - Zhou, W. - Zhu, X. - Zhu, Y. H. - Zoulkarneev, R. - Zoulkarneeva, Y.
Journal: Science

Nuclear collisions recreate conditions in the universe microseconds after the Big Bang. Only a very small fraction of the emitted fragments are light nuclei, but these states are of fundamental interest. We report the observation of antihypertritons-comprised of an antiproton, antineutron, and antilambda hyperon-produced by colliding gold nuclei at high energy. Our analysis yields 70 +/- 17 antihypertritons ($${}_{\overline{\Lambda }};{3}\overline{\mathrm{H}}$$) and 157 +/- 30 hypertritons ($${}_{\Lambda };{3}\mathrm{H}$$). The measured yields of $${}_{\Lambda };{3}\mathrm{H}$$ ($${}_{\overline{\Lambda }};{3}\overline{\mathrm{H}}$$) and (3)He ((3)$$\overline{\mathrm{He}}$$) are similar, suggesting an equilibrium in coordinate and momentum space populations of up, down, and strange quarks and antiquarks, unlike the pattern observed at lower collision energies. The production and properties of antinuclei, and nuclei containing strange quarks, have implications spanning nuclear/particle physics, astrophysics, and cosmology.

post to: CiteULike

Cortical plasticity induced by inhibitory neuron transplantation.

Publication Date: 2010 Feb 26 PMID: 20185728
Authors: Southwell, D. G. - Froemke, R. C. - Alvarez-Buylla, A. - Stryker, M. P. - Gandhi, S. P.
Journal: Science

Critical periods are times of pronounced brain plasticity. During a critical period in the postnatal development of the visual cortex, the occlusion of one eye triggers a rapid reorganization of neuronal responses, a process known as ocular dominance plasticity. We have shown that the transplantation of inhibitory neurons induces ocular dominance plasticity after the critical period. Transplanted inhibitory neurons receive excitatory synapses, make inhibitory synapses onto host cortical neurons, and promote plasticity when they reach a cellular age equivalent to that of endogenous inhibitory neurons during the normal critical period. These findings suggest that ocular dominance plasticity is regulated by the execution of a maturational program intrinsic to inhibitory neurons. By inducing plasticity, inhibitory neuron transplantation may facilitate brain repair.

post to: CiteULike

Noise can induce bimodality in positive transcriptional feedback loops without bistability.

Publication Date: 2010 Feb 26 PMID: 20185727
Authors: To, T. L. - Maheshri, N.
Journal: Science

Transcriptional positive-feedback loops are widely associated with bistability, characterized by two stable expression states that allow cells to respond to analog signals in a digital manner. Using a synthetic system in budding yeast, we show that positive feedback involving a promoter with multiple transcription factor (TF) binding sites can induce a steady-state bimodal response without cooperative binding of the TF. Deterministic models of this system do not predict bistability. Rather, the bimodal response requires a short-lived TF and stochastic fluctuations in the TF's expression. Multiple binding sites provide these fluctuations. Because many promoters possess multiple binding sites and many TFs are unstable, positive-feedback loops in gene regulatory networks may exhibit bimodal responses, but not necessarily because of deterministic bistability, as is commonly thought.

post to: CiteULike

Photorhabdus luminescens toxins ADP-ribosylate actin and RhoA to force actin clustering.

Publication Date: 2010 Feb 26 PMID: 20185726
Authors: Lang, A. E. - Schmidt, G. - Schlosser, A. - Hey, T. D. - Larrinua, I. M. - Sheets, J. J. - Mannherz, H. G. - Aktories, K.
Journal: Science

The bacterium Photorhabdus luminescens is mutualistically associated with entomopathogenetic nematodes. These nematodes invade insect larvae and release the bacteria from their intestine, which kills the insects through the action of toxin complexes. We elucidated the mode of action of two of these insecticidal toxins from P. luminescens. We identified the biologically active components TccC3 and TccC5 as adenosine diphosphate (ADP)-ribosyltransferases, which modify unusual amino acids. TccC3 ADP-ribosylated threonine-148 of actin, resulting in actin polymerization. TccC5 ADP-ribosylated Rho guanosine triphosphatase proteins at glutamine-61 and glutamine-63, inducing their activation. The concerted action of both toxins inhibited phagocytosis of target insect cells and induced extensive intracellular polymerization and clustering of actin. Several human pathogenic bacteria produce related toxins.

post to: CiteULike

Inhibition of NF-kappaB signaling by A20 through disruption of ubiquitin enzyme complexes.

Publication Date: 2010 Feb 26 PMID: 20185725
Authors: Shembade, N. - Ma, A. - Harhaj, E. W.
Journal: Science

A20 negatively regulates inflammation by inhibiting the nuclear factor kappaB (NF-kappaB) transcription factor in the tumor necrosis factor-receptor (TNFR) and Toll-like receptor (TLR) pathways. A20 contains deubiquitinase and E3 ligase domains and thus has been proposed to function as a ubiquitin-editing enzyme downstream of TNFR1 by inactivating ubiquitinated RIP1. However, it remains unclear how A20 terminates NF-kappaB signaling downstream of TLRs. We have shown that A20 inhibited the E3 ligase activities of TRAF6, TRAF2, and cIAP1 by antagonizing interactions with the E2 ubiquitin conjugating enzymes Ubc13 and UbcH5c. A20, together with the regulatory molecule TAX1BP1, interacted with Ubc13 and UbcH5c and triggered their ubiquitination and proteasome-dependent degradation. These findings suggest mechanism of A20 action in the inhibition of inflammatory signaling pathways.

post to: CiteULike

Individuals and the variation needed for high species diversity in forest trees.

Publication Date: 2010 Feb 26 PMID: 20185724
Authors: Clark, J. S.
Journal: Science

In the past, explanations for high species diversity have been sought at the species level. Theory shows that coexistence requires substantial differences between species, but species-level data rarely provide evidence for such differences. Using data from forests in the southeastern United States, I show here that variation evident at the individual level provides for coexistence of large numbers of competitors. Variation among individuals within populations allows species to differ in their distributions of responses to the environment, despite the fact that the populations to which they belong do not differ, on average. Results are consistent with theory predicting that coexistence depends on competition being stronger within than between species, shown here by analysis of individual-level responses to environmental fluctuation.

post to: CiteULike

A nodule-specific protein secretory pathway required for nitrogen-fixing symbiosis.

Publication Date: 2010 Feb 26 PMID: 20185723
Authors: Wang, D. - Griffitts, J. - Starker, C. - Fedorova, E. - Limpens, E. - Ivanov, S. - Bisseling, T. - Long, S.
Journal: Science

The nitrogen-fixing symbiosis between Sinorhizobium meliloti and its leguminous host plant Medicago truncatula occurs in a specialized root organ called the nodule. Bacteria that are released into plant cells are surrounded by a unique plant membrane compartment termed a symbiosome. We found that in the symbiosis-defective dnf1 mutant of M. truncatula, bacteroid and symbiosome development are blocked. We identified the DNF1 gene as encoding a subunit of a signal peptidase complex that is highly expressed in nodules. By analyzing data from whole-genome expression analysis, we propose that correct symbiosome development in M. truncatula requires the orderly secretion of protein constituents through coordinated up-regulation of a nodule-specific pathway exemplified by DNF1.

post to: CiteULike

Plant peptides govern terminal differentiation of bacteria in symbiosis.

Publication Date: 2010 Feb 26 PMID: 20185722
Authors: Van de Velde, W. - Zehirov, G. - Szatmari, A. - Debreczeny, M. - Ishihara, H. - Kevei, Z. - Farkas, A. - Mikulass, K. - Nagy, A. - Tiricz, H. - Satiat-Jeunemaitre, B. - Alunni, B. - Bourge, M. - Kucho, K. - Abe, M. - Kereszt, A. - Maroti, G. - Uchiumi, T. - Kondorosi, E. - Mergaert, P.
Journal: Science

Legume plants host nitrogen-fixing endosymbiotic Rhizobium bacteria in root nodules. In Medicago truncatula, the bacteria undergo an irreversible (terminal) differentiation mediated by hitherto unidentified plant factors. We demonstrated that these factors are nodule-specific cysteine-rich (NCR) peptides that are targeted to the bacteria and enter the bacterial membrane and cytosol. Obstruction of NCR transport in the dnf1-1 signal peptidase mutant correlated with the absence of terminal bacterial differentiation. On the contrary, ectopic expression of NCRs in legumes devoid of NCRs or challenge of cultured rhizobia with peptides provoked symptoms of terminal differentiation. Because NCRs resemble antimicrobial peptides, our findings reveal a previously unknown innovation of the host plant, which adopts effectors of the innate immune system for symbiosis to manipulate the cell fate of endosymbiotic bacteria.

post to: CiteULike

Integrated catalytic conversion of gamma-valerolactone to liquid alkenes for transportation fuels.

Publication Date: 2010 Feb 26 PMID: 20185721
Authors: Bond, J. Q. - Alonso, D. M. - Wang, D. - West, R. M. - Dumesic, J. A.
Journal: Science

Efficient synthesis of renewable fuels remains a challenging and important line of research. We report a strategy by which aqueous solutions of gamma-valerolactone (GVL), produced from biomass-derived carbohydrates, can be converted to liquid alkenes in the molecular weight range appropriate for transportation fuels by an integrated catalytic system that does not require an external source of hydrogen. The GVL feed undergoes decarboxylation at elevated pressures (e.g., 36 bar) over a silica/alumina catalyst to produce a gas stream composed of equimolar amounts of butene and carbon dioxide. This stream is fed directly to an oligomerization reactor containing an acid catalyst (e.g., H ZSM-5, Amberlyst-70), which couples butene monomers to form condensable alkenes with molecular weights that can be targeted for gasoline and/or jet fuel applications. The effluent gaseous stream of CO2 at elevated pressure can potentially be captured and then treated or sequestered to mitigate greenhouse gas emissions from the process.

post to: CiteULike

Mechanisms underlying lineage commitment and plasticity of helper CD4+ T cells.

Publication Date: 2010 Feb 26 PMID: 20185720
Authors: O'Shea, J. J. - Paul, W. E.
Journal: Science

CD4+ T cells are critical for host defense but are also major drivers of immune-mediated disease. These T cells specialize to become distinct subsets and produce restricted patterns of cytokines, which are tailored to combat various microbial pathogens. Although classically viewed as distinct lineages, recent work calls into question whether helper CD4+ T cell subsets are more appropriately viewed as terminally differentiated cells or works in progress. Herein, we review recent advances that pertain to this topic and the mechanisms that contribute to helper CD4+ T cell commitment and plasticity. The therapeutic implications of these new findings are also considered.

post to: CiteULike

SPORE: Science Prize for Online Resources in Education. On the Cutting Edge: teaching help for geoscience faculty.

Publication Date: 2010 Feb 26 PMID: 20185719
Authors: Manduca, C. A. - Mogk, D. W. - Tewksbury, B. - Macdonald, R. H. - Fox, S. P. - Iverson, E. R. - Kirk, K. - McDaris, J. - Ormand, C. - Bruckner, M.
Journal: Science

post to: CiteULike

Cell biology. Turning off inflammation signaling.

Publication Date: 2010 Feb 26 PMID: 20185718
Authors: Sriskantharajah, S. - Ley, S. C.
Journal: Science

post to: CiteULike

Climate. Seawater chemistry and climate.

Publication Date: 2010 Feb 26 PMID: 20185717
Authors: Elderfield, H.
Journal: Science

post to: CiteULike

Biochemistry. What makes a prion infectious?

Publication Date: 2010 Feb 26 PMID: 20185716
Authors: Supattapone, S.
Journal: Science

post to: CiteULike

Geophysics. Changing views of the San Andreas Fault.

Publication Date: 2010 Feb 26 PMID: 20185715
Authors: Scharer, K.
Journal: Science

post to: CiteULike

Molecular biology. Reliable noise.

Publication Date: 2010 Feb 26 PMID: 20185714
Authors: Levens, D. - Gupta, A.
Journal: Science

post to: CiteULike

Engineering. Intelligent infrastructure for energy efficiency.

Publication Date: 2010 Feb 26 PMID: 20185713
Authors: Gershenfeld, N. - Samouhos, S. - Nordman, B.
Journal: Science

post to: CiteULike

Atmospheric science. Observing weather from space.

Publication Date: 2010 Feb 26 PMID: 20185712
Authors: Kidder, S. Q. - Vonder Haar, T. H.
Journal: Science

post to: CiteULike

Life in science. The cow ate my fieldwork.

Publication Date: 2010 Feb 26 PMID: 20185711
Authors: Madsen, B. L.
Journal: Science

post to: CiteULike

The permanence debate.

Publication Date: 2010 Feb 26 PMID: 20185710
Authors: Skutsch, M. - de Jong, B. H.
Journal: Science

post to: CiteULike

Sowing the seeds of soil conservation.

Publication Date: 2010 Feb 26 PMID: 20185709
Authors: Lin, H.
Journal: Science

post to: CiteULike

Spain's budget neglects research.

Publication Date: 2010 Feb 26 PMID: 20185708
Authors: Afonso Alvarez, X. - Cabrera-Poch, N. - Canda-Sanchez, A. - Fenollosa, C. - Pinero, E. - van Raaij, M. J. - Sanchez Cobos, E. - Segura Perez, I. - Tapiador, F. J. - Torrado Agrasar, A. M.
Journal: Science

post to: CiteULike

Animal research. Dog dealers' days may be numbered.

Publication Date: 2010 Feb 26 PMID: 20185707
Authors: Grimm, D.
Journal: Science

post to: CiteULike

Planetary science. Iceball Mars proving a tough place to find liquid water.

Publication Date: 2010 Feb 26 PMID: 20185706
Authors: Kerr, R. A.
Journal: Science

post to: CiteULike

Medicine. Keeping tabs on tumor DNA.

Publication Date: 2010 Feb 26 PMID: 20185705
Authors: Kaiser, J.
Journal: Science

post to: CiteULike

Medicine. Cancer's circulation problem.

Publication Date: 2010 Feb 26 PMID: 20185704
Authors: Kaiser, J.
Journal: Science

post to: CiteULike

Meeting briefs. More highlights from AAAS 2010.

Publication Date: 2010 Feb 26 PMID: 20185703
Authors:
Journal: Science

post to: CiteULike

Meeting briefs. Scientists grapple with 'completely out of hand' attacks on climate science.

Publication Date: 2010 Feb 26 PMID: 20185702
Authors: Kintisch, E.
Journal: Science

post to: CiteULike

Meeting briefs. The latest on geoengineering.

Publication Date: 2010 Feb 26 PMID: 20185701
Authors: Kintisch, E.
Journal: Science

post to: CiteULike

Meeting briefs. Is a dolphin a person?

Publication Date: 2010 Feb 26 PMID: 20185700
Authors: Grimm, D.
Journal: Science

post to: CiteULike

STEM education. DOE reworks student initiative to prepare energy researchers.

Publication Date: 2010 Feb 26 PMID: 20185699
Authors: Mervis, J.
Journal: Science

post to: CiteULike

Psychiatry. Experts map the terrain of mood disorders.

Publication Date: 2010 Feb 26 PMID: 20185697
Authors: Holden, C.
Journal: Science

post to: CiteULike

Psychiatry. Suicide scale.

Publication Date: 2010 Feb 26 PMID: 20185696
Authors: Holden, C.
Journal: Science

post to: CiteULike

Physics. Century-long debate over momentum of light resolved?

Publication Date: 2010 Feb 26 PMID: 20185695
Authors: Cho, A.
Journal: Science

post to: CiteULike

Drug safety. New network to track drugs and vaccines in pregnancy.

Publication Date: 2010 Feb 26 PMID: 20185694
Authors: Couzin-Frankel, J.
Journal: Science

post to: CiteULike

Science to bridge the Americas.

Publication Date: 2010 Feb 26 PMID: 20185693
Authors: DeVoogd, T. J.
Journal: Science

post to: CiteULike

CKAMP44: A Brain-Specific Protein Attenuating Short-Term Synaptic Plasticity in the Dentate Gyrus.

Publication Date: 2010 Feb 25 PMID: 20185686
Authors: von Engelhardt, J. - Mack, V. - Sprengel, R. - Kavenstock, N. - Li, K. W. - Stern-Bach, Y. - Smit, A. B. - Seeburg, P. H. - Monyer, H.
Journal: Science

CKAMP44, identified here by a proteomic approach, is a brain-specific type I transmembrane protein that associates with AMPA receptors in synaptic spines. CKAMP44 expressed in Xenopus oocytes reduces GluA1- and A2-mediated steady-state currents, but fails to affect kainate- or NMDA receptor-mediated currents. Mouse hippocampal CA1 pyramidal neurons express CKAMP44 at low levels, and overexpression of CKAMP44 leads to stronger and faster AMPA receptor desensitization, slower recovery from desensitization, and a reduction in the paired-pulse ratio of AMPA currents. In contrast, dentate gyrus granule cells exhibit strong CKAMP44 expression, and here, CKAMP44 knockout increases the paired-pulse ratio of AMPA currents in lateral and medial perforant path-granule cell synapses. CKAMP44 thus modulates short-term plasticity at specific excitatory synapses.

post to: CiteULike

{beta}2-Adrenergic Receptor Redistribution in Heart Failure Changes cAMP Compartmentation.

Publication Date: 2010 Feb 25 PMID: 20185685
Authors: Nikolaev, V. O. - Moshkov, A. - Lyon, A. R. - Miragoli, M. - Novak, P. - Paur, H. - Lohse, M. J. - Korchev, Y. E. - Harding, S. E. - Gorelik, J.
Journal: Science

The beta(1)- and beta(2)-adrenergic receptors (betaARs) on the surface of cardiomyocytes mediate distinct effects on cardiac function and the development of heart failure by regulating production of the second messenger adenosine 3',5'-monophosphate (cAMP). The spatial localization in cardiomyocytes of these betaARs, which are coupled to heterotrimeric guanine nucleotide-binding protein (G protein), and the functional implications of their localization have been unclear. We combined nanoscale live-cell scanning ion conductance and fluorescence resonance energy transfer microscopy techniques and found that, in cardiomyocytes from healthy adult rats and mice, spatially confined beta(2)AR-induced cAMP signals are localized exclusively to the deep transverse tubules, whereas functional beta(1)ARs are distributed across the entire cell surface. In cardiomyocytes derived from a rat model of chronic heart failure, beta(2)ARs were redistributed from the transverse tubules to the cell crest, which led to diffuse receptor-mediated cAMP signaling. Thus, the redistribution of beta(2)ARs in heart failure changes compartmentation of cAMP and might contribute to the failing myocardial phenotype.

post to: CiteULike

Patterns of Diversity in Marine Phytoplankton.

Publication Date: 2010 Feb 25 PMID: 20185684
Authors: Barton, A. D. - Dutkiewicz, S. - Flierl, G. - Bragg, J. - Follows, M.
Journal: Science

Spatial diversity gradients are a pervasive feature of life on Earth. We examined a global ocean circulation, biogeochemistry, and ecosystem model that indicated a decrease in phytoplankton diversity with increasing latitude, consistent with observations of many marine and terrestrial taxa. In the modeled subpolar oceans, seasonal variability of the environment led to competitive exclusion of phytoplankton with slower growth rates and lower diversity. The relatively weak seasonality of the stable subtropical and tropical oceans in the global model enabled long exclusion time scales and prolonged coexistence of multiple phytoplankton with comparable fitness. Superimposed on the decline in diversity seen from equator to pole were "hot spots" of enhanced diversity in some regions of energetic ocean circulation, which reflected lateral dispersal.

post to: CiteULike

Constraints on the Formation Age of Cometary Material from the NASA Stardust Mission.

Publication Date: 2010 Feb 25 PMID: 20185683
Authors: Matzel, J. E. - Ishii, H. A. - Joswiak, D. - Hutcheon, I. D. - Bradley, J. P. - Brownlee, D. - Weber, P. K. - Teslich, N. - Matrajt, G. - McKeegan, K. D. - Macpherson, G. J.
Journal: Science

We measured the (26)Al-(26)Mg isotope systematics of a ~5-mum refractory particle, Coki, returned from comet 81P/Wild 2 in order to relate the time scales of formation of cometary inclusions to their meteoritic counterparts. The data show no evidence of radiogenic (26)Mg and define an upper limit to the abundance of (26)Al at the time of particle formation of (26)Al/(27)Al <1 x 10(-5). The absence of (26)Al indicates Coki formed >1.7 Ma after the oldest solar system solids, Ca-Al-rich inclusions (CAIs). The data presented here suggest that high temperature inner solar system material formed, was subsequently transferred to the Kuiper Belt, and incorporated into comets several million years following CAI formation.

post to: CiteULike

Unicellular Cyanobacterial Distributions Broaden the Oceanic N2 Fixation Domain.

Publication Date: 2010 Feb 25 PMID: 20185682
Authors: Moisander, P. H. - Beinart, R. A. - Hewson, I. - White, A. E. - Johnson, K. S. - Carlson, C. A. - Montoya, J. P. - Zehr, J. P.
Journal: Science

Nitrogen (N(2))-fixing microorganisms (diazotrophs) are an important source of biologically available fixed N in terrestrial and aquatic ecosystems, and control the productivity of oligotrophic ocean ecosystems (1, 2). We found that two major groups of unicellular N(2)-fixing cyanobacteria (UCYN) have distinct spatial distributions that differ from those of Trichodesmium, the N(2)-fixing cyanobacterium previously considered to be the most significant contributor to open ocean N(2) fixation. The distributions and activity of the two UCYN were separated as a function of depth, temperature, and water column density structure along a 8000 km transect in the South Pacific Ocean. UCYN-A can be found at high abundances at substantially higher latitudes and deeper in subsurface ocean waters than Trichodesmium. These findings have implications for the geographic extent and basin-scale oceanic N(2) fixation rates.

post to: CiteULike

Limits of predictability in human mobility.

Publication Date: 2010 Feb 19 PMID: 20167789
Authors: Song, C. - Qu, Z. - Blumm, N. - Barabasi, A. L.
Journal: Science

A range of applications, from predicting the spread of human and electronic viruses to city planning and resource management in mobile communications, depend on our ability to foresee the whereabouts and mobility of individuals, raising a fundamental question: To what degree is human behavior predictable? Here we explore the limits of predictability in human dynamics by studying the mobility patterns of anonymized mobile phone users. By measuring the entropy of each individual's trajectory, we find a 93% potential predictability in user mobility across the whole user base. Despite the significant differences in the travel patterns, we find a remarkable lack of variability in predictability, which is largely independent of the distance users cover on a regular basis.

MeSH Categories: *Behavior, *Cellular Phone, Forecasting, *Human Activities, Humans, Locomotion, Models, Statistical, Probability, *Travel

post to: CiteULike

Peptidomimetic antibiotics target outer-membrane biogenesis in Pseudomonas aeruginosa.

Publication Date: 2010 Feb 19 PMID: 20167788
Authors: Srinivas, N. - Jetter, P. - Ueberbacher, B. J. - Werneburg, M. - Zerbe, K. - Steinmann, J. - Van der Meijden, B. - Bernardini, F. - Lederer, A. - Dias, R. L. - Misson, P. E. - Henze, H. - Zumbrunn, J. - Gombert, F. O. - Obrecht, D. - Hunziker, P. - Schauer, S. - Ziegler, U. - Kach, A. - Eberl, L. - Riedel, K. - DeMarco, S. J. - Robinson, J. A.
Journal: Science

Antibiotics with new mechanisms of action are urgently required to combat the growing health threat posed by resistant pathogenic microorganisms. We synthesized a family of peptidomimetic antibiotics based on the antimicrobial peptide protegrin I. Several rounds of optimization gave a lead compound that was active in the nanomolar range against Gram-negative Pseudomonas spp., but was largely inactive against other Gram-negative and Gram-positive bacteria. Biochemical and genetic studies showed that the peptidomimetics had a non-membrane-lytic mechanism of action and identified a homolog of the beta-barrel protein LptD (Imp/OstA), which functions in outer-membrane biogenesis, as a cellular target. The peptidomimetic showed potent antimicrobial activity in a mouse septicemia infection model. Drug-resistant strains of Pseudomonas are a serious health problem, so this family of antibiotics may have important therapeutic applications.

MeSH Categories: Animals, Anti-Bacterial Agents/chemical synthesis/metabolism/*pharmacology, Antimicrobial Cationic Peptides/chemistry, Bacterial Outer Membrane Proteins/chemistry/genetics/*metabolism, Cell Membrane/*metabolism, Drug Design, Drug Resistance, Bacterial/genetics, Genes, Bacterial, Lipopolysaccharides/metabolism, Mice, Microbial Sensitivity Tests, Molecular Mimicry, Mutation, Peptide Library, Peptides/chemical synthesis/chemistry/metabolism/*pharmacology, Protein Structure, Tertiary, Pseudomonas Infections/drug therapy/microbiology, Pseudomonas aeruginosa/*drug effects/growth &, development/*metabolism/ultrastructure, Sepsis/drug therapy/microbiology

post to: CiteULike

Acetylation of metabolic enzymes coordinates carbon source utilization and metabolic flux.

Publication Date: 2010 Feb 19 PMID: 20167787
Authors: Wang, Q. - Zhang, Y. - Yang, C. - Xiong, H. - Lin, Y. - Yao, J. - Li, H. - Xie, L. - Zhao, W. - Yao, Y. - Ning, Z. B. - Zeng, R. - Xiong, Y. - Guan, K. L. - Zhao, S. - Zhao, G. P.
Journal: Science

Lysine acetylation regulates many eukaryotic cellular processes, but its function in prokaryotes is largely unknown. We demonstrated that central metabolism enzymes in Salmonella were acetylated extensively and differentially in response to different carbon sources, concomitantly with changes in cell growth and metabolic flux. The relative activities of key enzymes controlling the direction of glycolysis versus gluconeogenesis and the branching between citrate cycle and glyoxylate bypass were all regulated by acetylation. This modulation is mainly controlled by a pair of lysine acetyltransferase and deacetylase, whose expressions are coordinated with growth status. Reversible acetylation of metabolic enzymes ensure that cells respond environmental changes via promptly sensing cellular energy status and flexibly altering reaction rates or directions. It represents a metabolic regulatory mechanism conserved from bacteria to mammals.

MeSH Categories: Acetylation, Acetyltransferases/chemistry/genetics/metabolism, Amino Acid Sequence, Bacterial Proteins/*metabolism, Citric Acid/*metabolism, Energy Metabolism, Enzymes/*metabolism, Gene Expression Regulation, Bacterial, *Gluconeogenesis, Glucose/*metabolism, Glyceraldehyde-3-Phosphate Dehydrogenases/metabolism, *Glycolysis, Group III Histone Deacetylases/genetics/metabolism, Isocitrate Lyase/metabolism, Lysine/metabolism, Metabolic Networks and Pathways, Multienzyme Complexes/metabolism, Mutation, Protein Processing, Post-Translational, Protein-Serine-Threonine Kinases/metabolism, Recombinant Proteins/metabolism, Salmonella typhimurium/enzymology/genetics/growth &, development/*metabolism

post to: CiteULike

Regulation of cellular metabolism by protein lysine acetylation.

Publication Date: 2010 Feb 19 PMID: 20167786
Authors: Zhao, S. - Xu, W. - Jiang, W. - Yu, W. - Lin, Y. - Zhang, T. - Yao, J. - Zhou, L. - Zeng, Y. - Li, H. - Li, Y. - Shi, J. - An, W. - Hancock, S. M. - He, F. - Qin, L. - Chin, J. - Yang, P. - Chen, X. - Lei, Q. - Xiong, Y. - Guan, K. L.
Journal: Science

Protein lysine acetylation has emerged as a key posttranslational modification in cellular regulation, in particular through the modification of histones and nuclear transcription regulators. We show that lysine acetylation is a prevalent modification in enzymes that catalyze intermediate metabolism. Virtually every enzyme in glycolysis, gluconeogenesis, the tricarboxylic acid (TCA) cycle, the urea cycle, fatty acid metabolism, and glycogen metabolism was found to be acetylated in human liver tissue. The concentration of metabolic fuels, such as glucose, amino acids, and fatty acids, influenced the acetylation status of metabolic enzymes. Acetylation activated enoyl-coenzyme A hydratase/3-hydroxyacyl-coenzyme A dehydrogenase in fatty acid oxidation and malate dehydrogenase in the TCA cycle, inhibited argininosuccinate lyase in the urea cycle, and destabilized phosphoenolpyruvate carboxykinase in gluconeogenesis. Our study reveals that acetylation plays a major role in metabolic regulation.

MeSH Categories: 3-Hydroxyacyl CoA Dehydrogenases/metabolism, Acetylation, Argininosuccinate Lyase/genetics/metabolism, Cell Line, Citric Acid Cycle, Enoyl-CoA Hydratase/metabolism, Enzymes/*metabolism, Fatty Acids/metabolism, Gluconeogenesis, Glycogen/metabolism, Glycolysis, Hepatocytes/enzymology/*metabolism, Humans, Intracellular Signaling Peptides and Proteins/metabolism, Isomerases/metabolism, Liver/enzymology/*metabolism, Lysine/*metabolism, Malate Dehydrogenase/metabolism, Multienzyme Complexes/metabolism, Oxidation-Reduction, Phosphoenolpyruvate Carboxykinase (GTP)/metabolism, *Protein Processing, Post-Translational, Proteins/*metabolism, Proteome, Urea/metabolism

post to: CiteULike

Climate, critters, and cetaceans: Cenozoic drivers of the evolution of modern whales.

Publication Date: 2010 Feb 19 PMID: 20167785
Authors: Marx, F. G. - Uhen, M. D.
Journal: Science

Modern cetaceans, a poster child of evolution, play an important role in the ocean ecosystem as apex predators and nutrient distributors, as well as evolutionary "stepping stones" for the deep sea biota. Recent discussions on the impact of climate change and marine exploitation on current cetacean populations may benefit from insights into what factors have influenced cetacean diversity in the past. Previous studies suggested that the rise of diatoms as dominant marine primary producers and global temperature change were key factors in the evolution of modern whales. Based on a comprehensive diversity data set, we show that much of observed cetacean paleodiversity can indeed be explained by diatom diversity in conjunction with variations in climate as indicated by oxygen stable isotope records (delta18O).

MeSH Categories: Animals, Biodiversity, *Cetacea/classification/physiology, *Climate Change, *Diatoms, *Ecosystem, *Evolution, Feeding Behavior, Food Chain, *Fossils, Geologic Sediments, Oceans and Seas, Seawater, Temperature, *Whales/classification/physiology

post to: CiteULike

100-million-year dynasty of giant planktivorous bony fishes in the Mesozoic seas.

Publication Date: 2010 Feb 19 PMID: 20167784
Authors: Friedman, M. - Shimada, K. - Martin, L. D. - Everhart, M. J. - Liston, J. - Maltese, A. - Triebold, M.
Journal: Science

Large-bodied suspension feeders (planktivores), which include the most massive animals to have ever lived, are conspicuously absent from Mesozoic marine environments. The only clear representatives of this trophic guild in the Mesozoic have been an enigmatic and apparently short-lived Jurassic group of extinct pachycormid fishes. Here, we report several new examples of these giant bony fishes from Asia, Europe, and North America. These fossils provide the first detailed anatomical information on this poorly understood clade and extend its range from the lower Middle Jurassic to the end of the Cretaceous, showing that this group persisted for more than 100 million years. Modern large-bodied, planktivorous vertebrates diversified after the extinction of pachycormids at the Cretaceous-Paleogene boundary, which is consistent with an opportunistic refilling of vacated ecospace.

MeSH Categories: Animals, Asia, Body Size, Bone and Bones/anatomy & histology, *Ecosystem, Europe, Evolution, Extinction, Biological, Feeding Behavior, *Fishes/anatomy & histology/classification/physiology, Fossils, Jaw/anatomy & histology, North America, Oceans and Seas, Phylogeny, *Plankton, *Seawater, Skull/anatomy & histology, Time

post to: CiteULike

Asymmetric cooperative catalysis of strong Bronsted acid-promoted reactions using chiral ureas.

Publication Date: 2010 Feb 19 PMID: 20167783
Authors: Xu, H. - Zuend, S. J. - Woll, M. G. - Tao, Y. - Jacobsen, E. N.
Journal: Science

Cationic organic intermediates participate in a wide variety of useful synthetic transformations, but their high reactivity can render selectivity in competing pathways difficult to control. Here, we describe a strategy for inducing enantioselectivity in reactions of protio-iminium ions, wherein a chiral catalyst interacts with the highly reactive intermediate through a network of noncovalent interactions. This interaction leads to an attenuation of the reactivity of the iminium ion and allows high enantioselectivity in cycloadditions with electron-rich alkenes (the Povarov reaction). A detailed experimental and computational analysis of this catalyst system has revealed the precise nature of the catalyst-substrate interactions and the likely basis for enantioinduction.

MeSH Categories: Acids/*chemistry, Alkenes/*chemistry, Benzenesulfonates/*chemistry, *Catalysis, Chemical Phenomena, Imines/*chemistry, Magnetic Resonance Spectroscopy, Protons, Stereoisomerism, Thiourea/analogs & derivatives/chemistry, Urea/*analogs & derivatives/*chemistry

post to: CiteULike

The silicate-mediated formose reaction: bottom-up synthesis of sugar silicates.

Publication Date: 2010 Feb 19 PMID: 20167782
Authors: Lambert, J. B. - Gurusamy-Thangavelu, S. A. - Ma, K.
Journal: Science

Understanding the mechanism of sugar formation and stabilization is important for constraining theories on the abiotic origin of complex biomolecules. Although previous studies have produced sugars from small molecules through the formose and related reactions, the product mixtures are complex and unstable. We have demonstrated that simple two- and three-carbon molecules (glycolaldehyde and glyceraldehyde), in the presence of aqueous sodium silicate, spontaneously form silicate complexes of four- and six-carbon sugars, respectively. Silicate selects for sugars with a specific stereochemistry and sequesters them from rapid decomposition. Given the abundance of silicate minerals, these observations suggest that formose-like reactions may provide a feasible pathway for the abiotic formation of biologically important sugars, such as ribose.

MeSH Categories: Acetaldehyde/*analogs & derivatives/chemistry, Carbohydrates/*chemical synthesis/chemistry, Chemical Processes, Dimerization, Formaldehyde/chemistry, Glyceraldehyde/*chemistry, Hexoses/*chemical synthesis/chemistry, Silicates/*chemistry, Spectrometry, Mass, Electrospray Ionization, Stereoisomerism, Temperature, Tetroses/*chemical synthesis/chemistry

post to: CiteULike

Tuning the dimensionality of the heavy fermion compound CeIn3.

Publication Date: 2010 Feb 19 PMID: 20167781
Authors: Shishido, H. - Shibauchi, T. - Yasu, K. - Kato, T. - Kontani, H. - Terashima, T. - Matsuda, Y.
Journal: Science

Condensed-matter systems that are both low-dimensional and strongly interacting often exhibit unusual electronic properties. Strongly correlated electrons with greatly enhanced effective mass are present in heavy fermion compounds, whose electronic structure is essentially three-dimensional. We realized experimentally a two-dimensional heavy fermion system, adjusting the dimensionality in a controllable fashion. Artificial superlattices of the antiferromagnetic heavy fermion compound CeIn3 and the conventional metal LaIn3 were grown epitaxially. By reducing the thickness of the CeIn3 layers, the magnetic order was suppressed and the effective electron mass was further enhanced. Heavy fermions confined to two dimensions display striking deviations from the standard Fermi liquid low-temperature electronic properties, and these are associated with the dimensional tuning of quantum criticality.

post to: CiteULike

Retrospective. Marshall Warren Nirenberg (1927-2010).

Publication Date: 2010 Feb 19 PMID: 20167780
Authors: Leder, P.
Journal: Science

MeSH Categories: *Genetic Code, History, 20th Century, History, 21st Century, Molecular Biology/*history, National Institutes of Health (U.S.)/history, Nobel Prize, United States

post to: CiteULike

Atmospheric science. Can we understand clouds without turbulence?

Publication Date: 2010 Feb 19 PMID: 20167779
Authors: Bodenschatz, E. - Malinowski, S. P. - Shaw, R. A. - Stratmann, F.
Journal: Science

post to: CiteULike

Physics. The lowdown on heavy fermions.

Publication Date: 2010 Feb 19 PMID: 20167778
Authors: Coleman, P.
Journal: Science

post to: CiteULike

Paleontology. On giant filter feeders.

Publication Date: 2010 Feb 19 PMID: 20167777
Authors: Cavin, L.
Journal: Science

MeSH Categories: Animals, Biodiversity, Climate, *Diatoms, Evolution, Extinction, Biological, Feeding Behavior, *Fishes/anatomy & histology/classification/physiology, Food Chain, *Fossils, Geologic Sediments, Phylogeny, *Whales/anatomy & histology/classification/physiology

post to: CiteULike

Cell biology. When the beginning marks the end.

Publication Date: 2010 Feb 19 PMID: 20167776
Authors: Mogk, A. - Bukau, B.
Journal: Science

MeSH Categories: Acetylation, Amino Acid Sequence, Homeostasis, Humans, Protein Processing, Post-Translational, Protein Stability, Proteins/chemistry/*metabolism, Saccharomyces cerevisiae/metabolism, Saccharomyces cerevisiae Proteins/*metabolism, Ubiquitin-Protein Ligases/metabolism

post to: CiteULike

Chemistry. Cooperativity tames reactive catalysts.

Publication Date: 2010 Feb 19 PMID: 20167775
Authors: Schreiner, P. R.
Journal: Science

MeSH Categories: Acids/*chemistry, *Catalysis, Models, Chemical, Organic Chemicals/*chemistry, Physicochemical Processes, Protons, Stereoisomerism, Thiourea/analogs & derivatives/*chemistry, Urea/analogs & derivatives/*chemistry

post to: CiteULike

Cell biology. Rise of the rival.

Publication Date: 2010 Feb 19 PMID: 20167774
Authors: Norvell, A. - McMahon, S. B.
Journal: Science

MeSH Categories: Acetyl Coenzyme A/metabolism, Acetylation, Acetylesterase/metabolism, Bacterial Proteins/*metabolism, Enzymes/*metabolism, Hepatocytes/enzymology/*metabolism, Humans, Lysine/*metabolism, Metabolic Networks and Pathways, Phosphorylation, Proteins/*metabolism, Salmonella enterica/enzymology/*metabolism

post to: CiteULike

Research ethics. NIH guidelines for stem cell research and gamete donors.

Publication Date: 2010 Feb 19 PMID: 20167773
Authors: Lo, B. - Parham, L. - Cedars, M. - Fisher, S. - Gates, E. - Giudice, L. - Halme, D. G. - Hershon, W. - Kriegstein, A. - Rao, R. - Roberts, C. - Wagner, R.
Journal: Science

MeSH Categories: Cell Line, Disclosure, Embryo Disposition/*ethics/standards, Embryo Research/*ethics, *Embryonic Stem Cells, Female, Fertilization in Vitro, *Guidelines as Topic, Humans, Informed Consent, *National Institutes of Health (U.S.), *Oocyte Donation, *Tissue Donors, United States

post to: CiteULike

Oil and water do mix.

Publication Date: 2010 Feb 19 PMID: 20167772
Authors: Kavanau, J. L.
Journal: Science

post to: CiteULike

Sustainable foresting: easier said than done.

Publication Date: 2010 Feb 19 PMID: 20167771
Authors: Schulze, E. D. - Schulze, I.
Journal: Science

MeSH Categories: Animals, Biodiversity, Climate Change, *Conservation of Natural Resources/economics, *Ecosystem, *Forestry/economics, Germany, *Trees/growth & development, Wood

post to: CiteULike

Responsible researchers required.

Publication Date: 2010 Feb 19 PMID: 20167770
Authors: Levinger, N. E. - Fisher, E. R.
Journal: Science

MeSH Categories: Biomedical Research/*standards, *Education, Graduate, Research/*standards, Research Personnel/*education

post to: CiteULike

2009 Visualization Challenge. Photography.

Publication Date: 2010 Feb 19 PMID: 20167769
Authors:
Journal: Science

post to: CiteULike

2009 Visualization Challenge. Informational graphics.

Publication Date: 2010 Feb 19 PMID: 20167768
Authors:
Journal: Science

post to: CiteULike

2009 Visualization Challenge. Noninteractive media.

Publication Date: 2010 Feb 19 PMID: 20167767
Authors:
Journal: Science

post to: CiteULike

2009 Visualization Challenge. Interactive media.

Publication Date: 2010 Feb 19 PMID: 20167766
Authors:
Journal: Science

post to: CiteULike

2009 Visualization Challenge. Illustration.

Publication Date: 2010 Feb 19 PMID: 20167765
Authors:
Journal: Science

post to: CiteULike

2009 Visualization Challenge.

Publication Date: 2010 Feb 19 PMID: 20167764
Authors: Nesbit, J. - Bradford, M.
Journal: Science

MeSH Categories: Animals, Art, *Awards and Prizes, Computer Graphics, Computer Simulation, Data Display, Humans, Multimedia, Photography, Video Recording

post to: CiteULike

Joint Mathematics Meeting, 13-16 January, San Francisco, California. What comes next?

Publication Date: 2010 Feb 19 PMID: 20167763
Authors: Cipra, B.
Journal: Science

post to: CiteULike

Joint Mathematics Meeting, 13-16 January, San Francisco, California. Politics as (un)usual.

Publication Date: 2010 Feb 19 PMID: 20167762
Authors: Cipra, B.
Journal: Science

post to: CiteULike

Joint Mathematics Meeting, 13-16 January, San Francisco, California. Perfection in a box.

Publication Date: 2010 Feb 19 PMID: 20167761
Authors: Cipra, B.
Journal: Science

post to: CiteULike

Bhutan. Improbable partners aim to bring biotechnology to a Himalayan kingdom.

Publication Date: 2010 Feb 19 PMID: 20167760
Authors: Stone, R.
Journal: Science

MeSH Categories: Bhutan, Biodiversity, *Biological Products, *Biotechnology, *Cordyceps, *Drug Discovery, Drug Industry, *Medicine, Traditional, Research

post to: CiteULike

China. Leprosy's last stand--or early days of a war of attrition?

Publication Date: 2010 Feb 19 PMID: 20167759
Authors: Stone, R.
Journal: Science

MeSH Categories: China/epidemiology, Drug Resistance, Bacterial, Drug Therapy, Combination, Humans, Leprostatic Agents/pharmacology/therapeutic use, Leprosy/diagnosis/drug therapy/*epidemiology, Mycobacterium leprae/drug effects, Prevalence, Rifampin/pharmacology/therapeutic use

post to: CiteULike

Public health. Brawling over mammography.

Publication Date: 2010 Feb 19 PMID: 20167758
Authors: Marshall, E.
Journal: Science

MeSH Categories: Adult, Advisory Committees, Age Factors, Breast Neoplasms/mortality/*radiography, *Early Detection of Cancer/adverse effects, Female, Humans, *Mammography/adverse effects, Middle Aged, Politics, Randomized Controlled Trials as Topic, United States

post to: CiteULike

Psychiatry. Behavioral addictions debut in proposed DSM-V.

Publication Date: 2010 Feb 19 PMID: 20167757
Authors: Holden, C.
Journal: Science

MeSH Categories: Behavior, Addictive/*classification/diagnosis, Brain/physiology, *Diagnostic and Statistical Manual of Mental Disorders, Eating Disorders/classification/diagnosis, Gambling/*psychology, Humans, Obsessive-Compulsive Disorder/classification/diagnosis, Reward, Terminology as Topic

post to: CiteULike

Newsmaker interview. Embattled U.K. scientist defends track record of climate center. Interview by Eli Kintisch.

Publication Date: 2010 Feb 19 PMID: 20167756
Authors: Jones, P.
Journal: Science

post to: CiteULike

U.S. immigration policy. Prominent Iranian scientist blocked from attending physics meeting.

Publication Date: 2010 Feb 19 PMID: 20167755
Authors: Bhattacharjee, Y.
Journal: Science

post to: CiteULike

Invasive species. Biologists rush to protect Great Lakes from onslaught of carp.

Publication Date: 2010 Feb 19 PMID: 20167753
Authors: Stokstad, E.
Journal: Science

MeSH Categories: Animals, *Carps, Conservation of Natural Resources, *Ecosystem, *Fishes, *Fresh Water, Great Lakes Region, Population Dynamics, Rivers, *Zooplankton

post to: CiteULike

China. Fear of MRI scans trips up brain researchers.

Publication Date: 2010 Feb 19 PMID: 20167752
Authors: Jiao, L.
Journal: Science

MeSH Categories: Attention Deficit Disorder with Hyperactivity/*physiopathology, *Biomedical Research, Brain/*physiopathology, Child, Child, Preschool, China, Humans, *Magnetic Resonance Imaging, *Parental Consent, *Patient Selection

post to: CiteULike

U.S. Congress. Ehlers's retirement called 'big loss' for science.

Publication Date: 2010 Feb 19 PMID: 20167750
Authors: Mervis, J.
Journal: Science

post to: CiteULike

Brazil. Race for cellulosic fuels spurs Brazilian research program.

Publication Date: 2010 Feb 19 PMID: 20167749
Authors: Regalado, A.
Journal: Science

MeSH Categories: *Biofuels, Brazil, *Cellulose, *Ethanol, *Research, *Saccharum

post to: CiteULike

Bridging science and society.

Publication Date: 2010 Feb 19 PMID: 20167748
Authors: Agre, P. - Leshner, A. I.
Journal: Science

MeSH Categories: Attitude, Consumer Participation, Culture, Humans, Public Opinion, Religion and Science, *Science, Sociology

post to: CiteULike

Design of Polymethine Dyes with Large Third-Order Optical Nonlinearities and Loss Figures of Merit.

Publication Date: 2010 Feb 18 PMID: 20167746
Authors: Hales, J. M. - Matichak, J. - Barlow, S. - Ohira, S. - Yesudas, K. - Bredas, J. L. - Perry, J. W. - Marder, S. R.
Journal: Science

All-optical switching applications require materials with large third-order nonlinearities and low nonlinear optical losses. We present a design approach that involves enhancing the real part of the third-order polarizability (gamma) of cyanine-like molecules through incorporation of polarizable chalcogen atoms into terminal groups, while controlling the molecular length to obtain favorable one- and two-photon absorption resonances that lead to suitably low optical loss and appreciable dispersion enhancement of Re(gamma). We implement this strategy in a soluble bis(selenopyrylium) heptamethine dye that exhibits a real part of gamma that is exceptionally large throughout the wavelength range used for telecommunications, and an imaginary part of gamma, a measure of nonlinear loss, that is two orders-of-magnitude smaller. This combination is critical in enabling low-power and high-contrast optical switching.

post to: CiteULike

Vibrio cholerae VpsT regulates matrix production and motility by directly sensing cyclic di-GMP.

Publication Date: 2010 Feb 12 PMID: 20150502
Authors: Krasteva, P. V. - Fong, J. C. - Shikuma, N. J. - Beyhan, S. - Navarro, M. V. - Yildiz, F. H. - Sondermann, H.
Journal: Science

Microorganisms can switch from a planktonic, free-swimming life-style to a sessile, colonial state, called a biofilm, which confers resistance to environmental stress. Conversion between the motile and biofilm life-styles has been attributed to increased levels of the prokaryotic second messenger cyclic di-guanosine monophosphate (c-di-GMP), yet the signaling mechanisms mediating such a global switch are poorly understood. Here we show that the transcriptional regulator VpsT from Vibrio cholerae directly senses c-di-GMP to inversely control extracellular matrix production and motility, which identifies VpsT as a master regulator for biofilm formation. Rather than being regulated by phosphorylation, VpsT undergoes a change in oligomerization on c-di-GMP binding.

MeSH Categories: Amino Acid Motifs, Bacterial Proteins/chemistry/genetics/*metabolism, Binding Sites, Biofilms/*growth & development, Crystallography, X-Ray, Cyclic GMP/*analogs & derivatives/metabolism, DNA, Bacterial/metabolism, Dimerization, Extracellular Matrix/*metabolism, Gene Expression Profiling, Gene Expression Regulation, Bacterial, Models, Molecular, Movement, Point Mutation, Polysaccharides, Bacterial/genetics/metabolism, Protein Folding, Protein Multimerization, Protein Structure, Tertiary, Signal Transduction, Transcription Factors/chemistry/genetics/*metabolism, Transcription, Genetic, Vibrio cholerae O1/cytology/genetics/*physiology

post to: CiteULike

Sea-level highstand 81,000 years ago in Mallorca.

Publication Date: 2010 Feb 12 PMID: 20150501
Authors: Dorale, J. A. - Onac, B. P. - Fornos, J. J. - Gines, J. - Gines, A. - Tuccimei, P. - Peate, D. W.
Journal: Science

Global sea level and Earth's climate are closely linked. Using speleothem encrustations from coastal caves on the island of Mallorca, we determined that western Mediterranean relative sea level was approximately 1 meter above modern sea level approximately 81,000 years ago during marine isotope stage (MIS) 5a. Although our findings seemingly conflict with the eustatic sea-level curve of far-field sites, they corroborate an alternative view that MIS 5a was at least as ice-free as the present, and they challenge the prevailing view of MIS 5 sea-level history and certain facets of ice-age theory.

post to: CiteULike

Low-frequency modes of aqueous alkali halide solutions: glimpsing the hydrogen bonding vibration.

Publication Date: 2010 Feb 12 PMID: 20150500
Authors: Heisler, I. A. - Meech, S. R.
Journal: Science

The solvation of ions in aqueous media is a fundamental process in biology and chemistry. Here, we report direct time-domain observations of the hydrogen bond vibrational mode formed between a halide ion (chloride, bromide, or iodide) and the surrounding water molecules. The frequency of the hydrogen bond mode is sensitive to both the atomic weight and the concentration of the ion. The peak frequencies fall in the 125 to 175 wave-number range, a spectral region accessed through time-domain polarization-resolved coherent Raman scattering using a diffractive optic method. The polarized Raman response observed is discussed in terms of the structure of the anion's solvation shell and modeled through calculations on water chloride clusters.

post to: CiteULike

Quantum-state controlled chemical reactions of ultracold potassium-rubidium molecules.

Publication Date: 2010 Feb 12 PMID: 20150499
Authors: Ospelkaus, S. - Ni, K. K. - Wang, D. - de Miranda, M. H. - Neyenhuis, B. - Quemener, G. - Julienne, P. S. - Bohn, J. L. - Jin, D. S. - Ye, J.
Journal: Science

How does a chemical reaction proceed at ultralow temperatures? Can simple quantum mechanical rules such as quantum statistics, single partial-wave scattering, and quantum threshold laws provide a clear understanding of the molecular reactivity under a vanishing collision energy? Starting with an optically trapped near-quantum-degenerate gas of polar 40K87Rb molecules prepared in their absolute ground state, we report experimental evidence for exothermic atom-exchange chemical reactions. When these fermionic molecules were prepared in a single quantum state at a temperature of a few hundred nanokelvin, we observed p-wave-dominated quantum threshold collisions arising from tunneling through an angular momentum barrier followed by a short-range chemical reaction with a probability near unity. When these molecules were prepared in two different internal states or when molecules and atoms were brought together, the reaction rates were enhanced by a factor of 10 to 100 as a result of s-wave scattering, which does not have a centrifugal barrier. The measured rates agree with predicted universal loss rates related to the two-body van der Waals length.

post to: CiteULike

Break-up of stepped platinum catalyst surfaces by high CO coverage.

Publication Date: 2010 Feb 12 PMID: 20150498
Authors: Tao, F. - Dag, S. - Wang, L. W. - Liu, Z. - Butcher, D. R. - Bluhm, H. - Salmeron, M. - Somorjai, G. A.
Journal: Science

Stepped single-crystal surfaces are viewed as models of real catalysts, which consist of small metal particles exposing a large number of low-coordination sites. We found that stepped platinum (Pt) surfaces can undergo extensive and reversible restructuring when exposed to carbon monoxide (CO) at pressures above 0.1 torr. Scanning tunneling microscopy and photoelectron spectroscopy studies under gaseous environments near ambient pressure at room temperature revealed that as the CO surface coverage approaches 100%, the originally flat terraces of (557) and (332) oriented Pt crystals break up into nanometer-sized clusters and revert to the initial morphology after pumping out the CO gas. Density functional theory calculations provide a rationale for the observations whereby the creation of increased concentrations of low-coordination Pt edge sites in the formed nanoclusters relieves the strong CO-CO repulsion in the highly compressed adsorbate film. This restructuring phenomenon has important implications for heterogeneous catalytic reactions.

post to: CiteULike

Multiple functional groups of varying ratios in metal-organic frameworks.

Publication Date: 2010 Feb 12 PMID: 20150497
Authors: Deng, H. - Doonan, C. J. - Furukawa, H. - Ferreira, R. B. - Towne, J. - Knobler, C. B. - Wang, B. - Yaghi, O. M.
Journal: Science

We show that metal-organic frameworks (MOFs) can incorporate a large number of different functionalities on linking groups in a way that mixes the linker, rather than forming separate domains. We made complex MOFs from 1,4-benzenedicarboxylate (denoted by "A" in this work) and its derivatives -NH2, -Br, -(Cl)2, -NO2, -(CH3)2, -C4H4, -(OC3H5)2, and -(OC7H7)2 (denoted by "B" to "I," respectively) to synthesize 18 multivariate (MTV) MOF-5 type structures that contain up to eight distinct functionalities in one phase. The backbone (zinc oxide and phenylene units) of these structures is ordered, but the distribution of functional groups is disordered. The complex arrangements of several functional groups within the pores can lead to properties that are not simply linear sums of those of the pure components. For example, a member of this series, MTV-MOF-5-EHI, exhibits up to 400% better selectivity for carbon dioxide over carbon monoxide compared with its best same-link counterparts.

MeSH Categories: Carbon Dioxide/chemistry, Carbon Monoxide/chemistry, Chemical Phenomena, Crystallization, Crystallography, X-Ray, Magnetic Resonance Spectroscopy, Metals/*chemistry, Models, Chemical, Models, Molecular, Molecular Structure, Phthalic Acids/*chemistry, Zinc Oxide/*chemistry

post to: CiteULike

Spin-dependent quantum interference within a single magnetic nanostructure.

Publication Date: 2010 Feb 12 PMID: 20150496
Authors: Oka, H. - Ignatiev, P. A. - Wedekind, S. - Rodary, G. - Niebergall, L. - Stepanyuk, V. S. - Sander, D. - Kirschner, J.
Journal: Science

Quantum interference is a coherent quantum phenomenon that takes place in confined geometries. Using spin-polarized scanning tunneling microscopy, we found that quantum interference of electrons causes spatial modulation of spin polarization within a single magnetic nanostructure. We observed changes in both the sign and magnitude of the spin polarization on a subnanometer scale. A comparison of our experimental results with ab initio calculations shows that at a given energy, the modulation of the spin polarization can be ascribed to the difference between the spatially modulated local density of states of the majority spin and the nonmodulated minority spin contribution.

post to: CiteULike

Resonance fluorescence of a single artificial atom.

Publication Date: 2010 Feb 12 PMID: 20150495
Authors: Astafiev, O. - Zagoskin, A. M. - Abdumalikov, A. A. Jr - Pashkin, Y. A. - Yamamoto, T. - Inomata, K. - Nakamura, Y. - Tsai, J. S.
Journal: Science

An atom in open space can be detected by means of resonant absorption and reemission of electromagnetic waves, known as resonance fluorescence, which is a fundamental phenomenon of quantum optics. We report on the observation of scattering of propagating waves by a single artificial atom. The behavior of the artificial atom, a superconducting macroscopic two-level system, is in a quantitative agreement with the predictions of quantum optics for a pointlike scatterer interacting with the electromagnetic field in one-dimensional open space. The strong atom-field interaction as revealed in a high degree of extinction of propagating waves will allow applications of controllable artificial atoms in quantum optics and photonics.

post to: CiteULike

Radically rethinking agriculture for the 21st century.

Publication Date: 2010 Feb 12 PMID: 20150494
Authors: Fedoroff, N. V. - Battisti, D. S. - Beachy, R. N. - Cooper, P. J. - Fischhoff, D. A. - Hodges, C. N. - Knauf, V. C. - Lobell, D. - Mazur, B. J. - Molden, D. - Reynolds, M. P. - Ronald, P. C. - Rosegrant, M. W. - Sanchez, P. A. - Vonshak, A. - Zhu, J. K.
Journal: Science

Population growth, arable land and fresh water limits, and climate change have profound implications for the ability of agriculture to meet this century's demands for food, feed, fiber, and fuel while reducing the environmental impact of their production. Success depends on the acceptance and use of contemporary molecular techniques, as well as the increasing development of farming systems that use saline water and integrate nutrient flows.

MeSH Categories: Agriculture/legislation & jurisprudence/methods/*trends, Aquaculture/methods/trends, Biotechnology, Climate Change, *Crops, Agricultural, Food, Genetically Modified, Government Regulation, Population Growth, Private Sector, Public Sector, United States, United States Department of Agriculture

post to: CiteULike

African Green Revolution needn't be a mirage.

Publication Date: 2010 Feb 12 PMID: 20150493
Authors: Ejeta, G.
Journal: Science

Africa missed out on the scientific breakthroughs that revolutionized agriculture in Asia. However, with locally developed and locally relevant technologies, a built-up human and institutional capacity, and supportive national policy and leadership, an African Green Revolution can be a reality.

MeSH Categories: Africa South of the Sahara, *Agriculture/economics/education/methods/organization & administration, *Crops, Agricultural, Humans, International Cooperation, Public Policy, *Research

post to: CiteULike

Precision agriculture and food security.

Publication Date: 2010 Feb 12 PMID: 20150492
Authors: Gebbers, R. - Adamchuk, V. I.
Journal: Science

Precision agriculture comprises a set of technologies that combines sensors, information systems, enhanced machinery, and informed management to optimize production by accounting for variability and uncertainties within agricultural systems. Adapting production inputs site-specifically within a field and individually for each animal allows better use of resources to maintain the quality of the environment while improving the sustainability of the food supply. Precision agriculture provides a means to monitor the food production chain and manage both the quantity and quality of agricultural produce.

MeSH Categories: Agriculture/*methods, Animal Husbandry/*methods, Animals, Animals, Domestic, Automation, *Crops, Agricultural/growth & development, *Food Supply, *Soil

post to: CiteULike

Measuring food insecurity.

Publication Date: 2010 Feb 12 PMID: 20150491
Authors: Barrett, C. B.
Journal: Science

Food security is a growing concern worldwide. More than 1 billion people are estimated to lack sufficient dietary energy availability, and at least twice that number suffer micronutrient deficiencies. Because indicators inform action, much current research focuses on improving food insecurity measurement. Yet estimated prevalence rates and patterns remain tenuous because measuring food security, an elusive concept, remains difficult.

MeSH Categories: Diet, Food/*statistics & numerical data, Food Supply/*statistics & numerical data, Humans, Malnutrition/*epidemiology, Nutritional Status

post to: CiteULike

Smart investments in sustainable food production: revisiting mixed crop-livestock systems.

Publication Date: 2010 Feb 12 PMID: 20150490
Authors: Herrero, M. - Thornton, P. K. - Notenbaert, A. M. - Wood, S. - Msangi, S. - Freeman, H. A. - Bossio, D. - Dixon, J. - Peters, M. - van de Steeg, J. - Lynam, J. - Parthasarathy Rao, P. - Macmillan, S. - Gerard, B. - McDermott, J. - Sere, C. - Rosegrant, M.
Journal: Science

Farmers in mixed crop-livestock systems produce about half of the world's food. In small holdings around the world, livestock are reared mostly on grass, browse, and nonfood biomass from maize, millet, rice, and sorghum crops and in their turn supply manure and traction for future crops. Animals act as insurance against hard times and supply farmers with a source of regular income from sales of milk, eggs, and other products. Thus, faced with population growth and climate change, small-holder farmers should be the first target for policies to intensify production by carefully managed inputs of fertilizer, water, and feed to minimize waste and environmental impact, supported by improved access to markets, new varieties, and technologies.

MeSH Categories: *Agriculture/economics/methods/statistics & numerical data, *Animal Husbandry/economics/methods/statistics & numerical data, Animals, *Animals, Domestic, Conservation of Natural Resources, *Crops, Agricultural, Developing Countries, Ecosystem, Food Supply/economics/*statistics & numerical data, International Cooperation, Public-Private Sector Partnerships

post to: CiteULike

Breeding technologies to increase crop production in a changing world.

Publication Date: 2010 Feb 12 PMID: 20150489
Authors: Tester, M. - Langridge, P.
Journal: Science

To feed the several billion people living on this planet, the production of high-quality food must increase with reduced inputs, but this accomplishment will be particularly challenging in the face of global environmental change. Plant breeders need to focus on traits with the greatest potential to increase yield. Hence, new technologies must be developed to accelerate breeding through improving genotyping and phenotyping methods and by increasing the available genetic diversity in breeding germplasm. The most gain will come from delivering these technologies in developing countries, but the technologies will have to be economically accessible and readily disseminated. Crop improvement through breeding brings immense value relative to investment and offers an effective approach to improving food security.

MeSH Categories: Agriculture/*methods, *Biotechnology, *Breeding, Crops, Agricultural/*genetics/growth & development, Developing Countries, Environment, Food, Genetically Modified, Genes, Plant, Genetic Markers, Genetic Techniques, Genetic Variation, Genotype, Phenotype

post to: CiteULike

For more protein, filet of cricket.

Publication Date: 2010 Feb 12 PMID: 20150488
Authors: Vogel, G.
Journal: Science

MeSH Categories: Animals, *Dietary Proteins, *Food, Humans, *Insects, Nutritive Value

post to: CiteULike

Could less meat mean more food?

Publication Date: 2010 Feb 12 PMID: 20150487
Authors: Stokstad, E.
Journal: Science

MeSH Categories: *Cereals/economics/supply & distribution, Commerce, Computer Simulation, Developed Countries, Developing Countries, *Diet, Food Preferences, *Food Supply, Health, Humans, *Meat/economics/supply & distribution

post to: CiteULike

What it takes to make that meal.

Publication Date: 2010 Feb 12 PMID: 20150486
Authors:
Journal: Science

MeSH Categories: *Agriculture, *Energy-Generating Resources, *Food, *Food Handling

post to: CiteULike

Dialing up knowledge--and harvests.

Publication Date: 2010 Feb 12 PMID: 20150485
Authors: Stone, R.
Journal: Science

MeSH Categories: *Agriculture/economics, *Cellular Phone, *Crops, Agricultural/economics, *Developing Countries, India, *Information Dissemination, *Internet, Rural Population

post to: CiteULike

Spoiling for a fight with mold.

Publication Date: 2010 Feb 12 PMID: 20150484
Authors: Normile, D.
Journal: Science

MeSH Categories: Aflatoxins/biosynthesis/toxicity, Australia, Crops, Agricultural/*microbiology, *Food Microbiology, *Fungi/metabolism, History, 20th Century, History, 21st Century, Humans, Mycotoxins/toxicity

post to: CiteULike

Holding back a torrent of rats.

Publication Date: 2010 Feb 12 PMID: 20150483
Authors: Normile, D.
Journal: Science

MeSH Categories: Animals, *Crops, Agricultural/growth & development, *Murinae, *Oryza sativa/growth & development, Population Dynamics, *Rats/physiology, *Rodent Control, Sasa/growth & development

post to: CiteULike

Armed and dangerous.

Publication Date: 2010 Feb 12 PMID: 20150482
Authors: Pennisi, E.
Journal: Science

MeSH Categories: *Crops, Agricultural/microbiology/virology, Fungi/pathogenicity, *Plant Diseases/economics/microbiology/statistics & numerical data/therapy, Potyviridae/pathogenicity

post to: CiteULike

Sowing the seeds for the ideal crop.

Publication Date: 2010 Feb 12 PMID: 20150481
Authors: Pennisi, E.
Journal: Science

MeSH Categories: Breeding, Chromosomes, Artificial, Chromosomes, Plant, *Crops, Agricultural/chemistry/genetics/growth & development, Genes, Plant, *Genetic Engineering, RNA Interference, *Robotics, Seeds/chemistry, Water

post to: CiteULike

China's push to add by subtracting fertilizer.

Publication Date: 2010 Feb 12 PMID: 20150480
Authors: Hvistendahl, M.
Journal: Science

MeSH Categories: Africa South of the Sahara, Agriculture/*methods, China, Crops, Agricultural/*growth & development, Fertilizers/*utilization

post to: CiteULike

Getting more drops to the crops.

Publication Date: 2010 Feb 12 PMID: 20150479
Authors: Vince, G.
Journal: Science

MeSH Categories: Africa, Agriculture/*methods, Crops, Agricultural/*growth & development, India, Rain, *Water, *Water Supply

post to: CiteULike

From one farmer, hope--and reason for worry.

Publication Date: 2010 Feb 12 PMID: 20150478
Authors: Vince, G.
Journal: Science

MeSH Categories: Agriculture/*methods, Crops, Agricultural/*growth & development, *Food Supply, Uganda

post to: CiteULike

Food security. Feeding the future. Introduction.

Publication Date: 2010 Feb 12 PMID: 20150477
Authors: Ash, C. - Jasny, B. R. - Malakoff, D. A. - Sugden, A. M.
Journal: Science

MeSH Categories: *Agriculture, Animals, *Food, *Food Supply, Humans, Malnutrition/epidemiology, Research

post to: CiteULike

Chemistry. Radical ligands confer nobility on base-metal catalysts.

Publication Date: 2010 Feb 12 PMID: 20150476
Authors: Chirik, P. J. - Wieghardt, K.
Journal: Science

post to: CiteULike

Microbiology. Feasting on minerals.

Publication Date: 2010 Feb 12 PMID: 20150475
Authors: Newman, D. K.
Journal: Science

MeSH Categories: Acidithiobacillus/growth & development/*metabolism, Bacteria/growth & development/*metabolism, Bacterial Proteins/metabolism, Carrier Proteins/metabolism, Cytochromes c/metabolism, Electron Transport, Energy Metabolism, Ferric Compounds/*metabolism, Ferrous Compounds/*metabolism/toxicity, Hydrogen-Ion Concentration, Oxidation-Reduction

post to: CiteULike

Genetics. Genetic control of hotspots.

Publication Date: 2010 Feb 12 PMID: 20150474
Authors: Cheung, V. G. - Sherman, S. L. - Feingold, E.
Journal: Science

MeSH Categories: Aneuploidy, Animals, Base Sequence, Chromatin/*metabolism, *Crossing Over, Genetic, DNA/chemistry/*metabolism, Genetic Association Studies, Genetic Variation, Heterozygote, Histone-Lysine N-Methyltransferase/*genetics/metabolism, Humans, Meiosis/*genetics, Mice, *Recombination, Genetic

post to: CiteULike

Climate change. Ice age rhythms.

Publication Date: 2010 Feb 12 PMID: 20150473
Authors: Edwards, R. L.
Journal: Science

post to: CiteULike

Chemistry. CO prefers the aisle seat.

Publication Date: 2010 Feb 12 PMID: 20150472
Authors: Altman, M. S.
Journal: Science

post to: CiteULike

Chemistry. Ultracold chemistry.

Publication Date: 2010 Feb 12 PMID: 20150471
Authors: Hutson, J. M.
Journal: Science

post to: CiteULike

Cell biology. Propelling progeny.

Publication Date: 2010 Feb 12 PMID: 20150470
Authors: Pickup, D. J.
Journal: Science

MeSH Categories: Actins/physiology, Animals, Cell Membrane/physiology/virology, Leukocytes/virology, Membrane Glycoproteins/metabolism, Mice, Microvilli/physiology/*virology, Models, Biological, Phosphorylation, Poxviridae/*physiology, Protein-Tyrosine Kinases/metabolism, Vaccinia virus/*physiology, Viral Envelope Proteins/metabolism, Viral Proteins/*metabolism, Viral Structural Proteins/metabolism, Virion/physiology, Virus Replication

post to: CiteULike

Economics. Sustainability and global seafood.

Publication Date: 2010 Feb 12 PMID: 20150469
Authors: Smith, M. D. - Roheim, C. A. - Crowder, L. B. - Halpern, B. S. - Turnipseed, M. - Anderson, J. L. - Asche, F. - Bourillon, L. - Guttormsen, A. G. - Khan, A. - Liguori, L. A. - McNevin, A. - O'Connor, M. I. - Squires, D. - Tyedmers, P. - Brownstein, C. - Carden, K. - Klinger, D. H. - Sagarin, R. - Selkoe, K. A.
Journal: Science

MeSH Categories: Animals, *Aquaculture/economics/legislation & jurisprudence/organization &, administration, *Commerce/legislation & jurisprudence, Developed Countries/economics, Developing Countries/economics, *Ecosystem, *Fisheries/economics/legislation & jurisprudence, *Fishes, Food Supply, Government, Humans, Malnutrition/epidemiology, *Seafood/economics, *Shellfish

post to: CiteULike

Stop listening to scientists?

Publication Date: 2010 Feb 12 PMID: 20150467
Authors: Gurney, K. R.
Journal: Science

post to: CiteULike

Carbon calculations to consider.

Publication Date: 2010 Feb 12 PMID: 20150466
Authors: Sorensen, B.
Journal: Science

MeSH Categories: *Biofuels, Biomass, *Carbon, *Climate Change, Wood

post to: CiteULike

Science and society. Lights! Camera! Science?

Publication Date: 2010 Feb 12 PMID: 20150465
Authors: Enserink, M.
Journal: Science

MeSH Categories: *Motion Pictures as Topic, *Science

post to: CiteULike

Society for Integrative and Comparative Biology, 3-7 January 2010, Seattle, Washington. Koalas calling.

Publication Date: 2010 Feb 12 PMID: 20150464
Authors: Pennisi, E.
Journal: Science

MeSH Categories: Animals, *Behavior, Animal, Female, Homing Behavior, Male, Phascolarctidae/*physiology/psychology, *Sexual Behavior, Animal, *Vocalization, Animal

post to: CiteULike

Society for Integrative and Comparative Biology, 3-7 January 2010, Seattle, Washington. Racing crash-happy cockroaches.

Publication Date: 2010 Feb 12 PMID: 20150463
Authors: Pennisi, E.
Journal: Science

MeSH Categories: Animals, Biomechanics, Locomotion, Periplaneta/*physiology, Robotics

post to: CiteULike

Society for Integrative and Comparative Biology, 3-7 January 2010, Seattle, Washington. Rattan stuck in a growth mode.

Publication Date: 2010 Feb 12 PMID: 20150462
Authors: Pennisi, E.
Journal: Science

MeSH Categories: Arecaceae/*anatomy & histology/*growth & development, Calamus/*anatomy & histology/*growth & development, Plant Leaves/anatomy & histology/growth & development, Plant Stems/anatomy & histology/growth & development

post to: CiteULike

Newsmaker interview. Down-to-earth science fiction. Interview by Elizabeth Pennisi.

Publication Date: 2010 Feb 12 PMID: 20150461
Authors: Wilson, E. O.
Journal: Science

MeSH Categories: Animals, *Ants, Biology, *Ecosystem, *Literature, Modern

post to: CiteULike

Immunology. Replacing an immune system gone haywire.

Publication Date: 2010 Feb 12 PMID: 20150460
Authors: Couzin-Frankel, J.
Journal: Science

MeSH Categories: Autoimmune Diseases/*therapy, Clinical Trials as Topic, *Hematopoietic Stem Cell Transplantation/adverse effects/mortality, Humans, Immune System/physiology, Recurrence, Remission Induction, Transplantation Conditioning

post to: CiteULike

Psychiatry. Proposed revisions to psychiatry's canon unveiled.

Publication Date: 2010 Feb 12 PMID: 20150459
Authors: Miller, G. - Holden, C.
Journal: Science

MeSH Categories: *Diagnostic and Statistical Manual of Mental Disorders, Humans, Mental Disorders/*classification/*diagnosis, Terminology as Topic

post to: CiteULike

Psychiatry. DSM-V at a glance.

Publication Date: 2010 Feb 12 PMID: 20150458
Authors:
Journal: Science

MeSH Categories: Adolescent, Child, *Diagnostic and Statistical Manual of Mental Disorders, Humans, Mental Disorders/*classification/diagnosis

post to: CiteULike

Newsmaker interview. IPCC seeks 'broader community engagement' to correct errors. Interview by Eli Kintisch.

Publication Date: 2010 Feb 12 PMID: 20150455
Authors: Field, C.
Journal: Science

post to: CiteULike

U.S. science policy. Bement to leave NSF before term ends.

Publication Date: 2010 Feb 12 PMID: 20150454
Authors: Mervis, J.
Journal: Science

post to: CiteULike

India. After acrimonious debate, India rejects GM eggplant.

Publication Date: 2010 Feb 12 PMID: 20150453
Authors: Bagla, P.
Journal: Science

MeSH Categories: Bacillus thuringiensis/genetics, Crops, Agricultural/*genetics, *Food, Genetically Modified, *Genetic Engineering, India, Pest Control, Biological, Public Opinion, Solanum melongena/*genetics

post to: CiteULike

Particle physics. New delay of Large Hadron Collider might not keep its rival on the job.

Publication Date: 2010 Feb 12 PMID: 20150452
Authors: Cho, A.
Journal: Science

post to: CiteULike

Reaping benefits of crop research.

Publication Date: 2010 Feb 12 PMID: 20150451
Authors: Baulcombe, D.
Journal: Science

MeSH Categories: *Agriculture/education, *Crops, Agricultural/genetics/physiology, Interdisciplinary Communication, International Cooperation, *Research

post to: CiteULike

Significant acidification in major Chinese croplands.

Publication Date: 2010 Feb 19 PMID: 20150447
Authors: Guo, J. H. - Liu, X. J. - Zhang, Y. - Shen, J. L. - Han, W. X. - Zhang, W. F. - Christie, P. - Goulding, K. W. - Vitousek, P. M. - Zhang, F. S.
Journal: Science

Soil acidification is a major problem in soils of intensive Chinese agricultural systems. We used two nationwide surveys, paired comparisons in numerous individual sites, and several long-term monitoring-field data sets to evaluate changes in soil acidity. Soil pH declined significantly (P < 0.001) from the 1980s to the 2000s in the major Chinese crop-production areas. Processes related to nitrogen cycling released 20 to 221 kilomoles of hydrogen ion (H+) per hectare per year, and base cations uptake contributed a further 15 to 20 kilomoles of H+ per hectare per year to soil acidification in four widespread cropping systems. In comparison, acid deposition (0.4 to 2.0 kilomoles of H+ per hectare per year) made a small contribution to the acidification of agricultural soils across China.

MeSH Categories: *Agriculture, Cations, China, Crops, Agricultural/*growth & development/metabolism, Fertilizers, Hydrogen-Ion Concentration, Nitrogen, *Soil, Time Factors

post to: CiteULike

Dark Matter Search Results from the CDMS II Experiment.

Publication Date: 2010 Feb 11 PMID: 20150446
Authors: Ahmed, Z. - Akerib, D. S. - Arrenberg, S. - Bailey, C. N. - Balakishiyeva, D. - Baudis, L. - Bauer, D. A. - Brink, P. L. - Bruch, T. - Bunker, R. - Cabrera, B. - Caldwell, D. O. - Cooley, J. - Cushman, P. - Daal, M. - Dejongh, F. - Dragowsky, M. R. - Duong, L. - Fallows, S. - Figueroa-Feliciano, E. - Filippini, J. - Fritts, M. - Golwala, S. R. - Grant, D. R. - Hall, J. - Hennings-Yeomans, R. - Hertel, S. A. - Holmgren, D. - Hsu, L. - Huber, M. E. - Kamaev, O. - Kiveni, M. - Kos, M. - Leman, S. W. - Mahapatra, R. - Mandic, V. - McCarthy, K. A. - Mirabolfathi, N. - Moore, D. - Nelson, H. - Ogburn, R. W. - Phipps, A. - Pyle, M. - Qiu, X. - Ramberg, E. - Rau, W. - Reisetter, A. - Saab, T. - Sadoulet, B. - Sander, J. - Schnee, R. W. - Seitz, D. N. - Serfass, B. - Sundqvist, K. M. - Tarka, M. - Wikus, P. - Yellin, S. - Yoo, J. - Young, B. A. - Zhang, J.
Journal: Science

Astrophysical observations indicate that dark matter constitutes most of the mass in our universe, but its nature remains unknown. Over the past decade, the Cryogenic Dark Matter Search (CDMS II) experiment has provided world-leading sensitivity for the direct detection of Weakly Interacting Massive Particle (WIMP) dark matter. The final exposure of our low-temperature Ge particle detectors at the Soudan Underground Laboratory yielded two candidate events, with an expected background of 0.9 +/- 0.2 events. This is not statistically significant evidence for a WIMP signal. The combined CDMS II data place the strongest constraints on the WIMP-nucleon spin-independent scattering cross section for a wide range of WIMP masses and exclude new parameter space in inelastic dark matter models.

post to: CiteULike

Intellectual property. Fixing the legal framework for pharmaceutical research.

Publication Date: 2010 Feb 26 PMID: 20150445
Authors: Knowles, S. M.
Journal: Science

post to: CiteULike

Doc2b Is a High-Affinity Ca2+ Sensor for Spontaneous Neurotransmitter Release.

Publication Date: 2010 Feb 11 PMID: 20150444
Authors: Groffen, A. J. - Martens, S. - Arazola, R. D. - Cornelisse, L. N. - Lozovaya, N. - de Jong, A. P. - Goriounova, N. A. - Habets, R. L. - Takai, Y. - Borst, J. G. - Brose, N. - McMahon, H. T. - Verhage, M.
Journal: Science

Synaptic vesicle fusion in brain synapses occurs in phases that are either tightly coupled to action potentials (synchronous), immediately following action potentials (asynchronous), or as stochastic events in the absence of action potentials (spontaneous). Synaptotagmin-1, -2 and -9 are vesicle-associated Ca(2+) sensors for synchronous release. Here we found that double C2 domain (Doc2) proteins act as Ca(2+) sensors to trigger spontaneous release. Although Doc2 proteins are cytosolic, they function analogously to synaptotagmin-1 but with a higher Ca(2+) sensitivity and superior in vitro fusion efficiency. Doc2 proteins bound to SNARE complexes in competition with synaptotagmin-1. Thus, different classes of multiple C2 domain-containing molecules trigger synchronous versus spontaneous fusion, which suggests a general mechanism for synaptic vesicle fusion triggered by the combined actions of SNAREs and multiple C2 domain-containing proteins.

post to: CiteULike

Light-Controlled Self-Assembly of Semiconductor Nanoparticles into Twisted Ribbons.

Publication Date: 2010 Feb 11 PMID: 20150443
Authors: Srivastava, S. - Santos, A. - Critchley, K. - Kim, K. S. - Podsiadlo, P. - Sun, K. - Lee, J. - Xu, C. - Lilly, G. D. - Glotzer, S. C. - Kotov, N. A.
Journal: Science

The collective properties of nanoparticles manifest in their ability to self-organize into complex microscale structures. Slow oxidation of Te(2-) in CdTe nanoparticles results in the assembly of 1 to 4-mum long flat ribbons made of several layers of individual CdS/CdTe nanocrystals. Twisting of the ribbons with an equal distribution of left and right-helices was induced by illumination with visible light. The pitch lengths (250 to 1500 nanometers) varied with illumination dose, and the twisting was associated with the relief of mechanical shear stress in assembled ribbons caused by photooxidation of CdS. Unusual shapes of multiparticle assemblies, such as ellipsoidal clouds, dog-bone agglomerates, and ribbon bunches, were observed as intermediate stages. Computer simulations revealed that the balance between attraction and electrostatic repulsion determines the resulting geometry and dimensionality of nanoparticles assemblies.

post to: CiteULike

A Stratified Redox Model for the Ediacaran Ocean.

Publication Date: 2010 Feb 11 PMID: 20150442
Authors: Li, C. - Love, G. D. - Lyons, T. W. - Fike, D. A. - Sessions, A. L. - Chu, X.
Journal: Science

The Ediacaran Period (635-542 million years ago) was a time of fundamental environmental and evolutionary change, culminating in the first appearance of macroscopic animals. Here we present a detailed spatial and temporal record of Ediacaran ocean chemistry for the Doushantuo Formation in the Nanhua Basin, South China. We find evidence for a metastable zone of euxinic (anoxic and sulfidic) waters impinging on the continental shelf and sandwiched within ferruginous [Fe(II)-enriched] deep waters. A stratified ocean with coeval oxic, sulfidic and ferruginous zones, favored by overall low oceanic sulfate concentrations, was maintained dynamically throughout the Ediacaran Period. Our model reconciles seemingly conflicting geochemical redox conditions proposed previously for Ediacaran deep oceans and helps explain the patchy temporal record of early metazoan fossils.

post to: CiteULike

Retromer is required for apoptotic cell clearance by phagocytic receptor recycling.

Publication Date: 2010 Mar 5 PMID: 20133524
Authors: Chen, D. - Xiao, H. - Zhang, K. - Wang, B. - Gao, Z. - Jian, Y. - Qi, X. - Sun, J. - Miao, L. - Yang, C.
Journal: Science

The cell surface receptor CED-1 mediates apoptotic cell recognition by phagocytic cells, enabling cell corpse clearance in Caenorhabditis elegans. Here, we found that the C. elegans intracellular protein sorting complex, retromer, was required for cell corpse clearance by mediating the recycling of CED-1. Retromer was recruited to the surfaces of phagosomes containing cell corpses, and its loss of function caused defective cell corpse removal. The retromer probably acted through direct interaction with CED-1 in the cell corpse recognition pathway. In the absence of retromer function, CED-1 associated with lysosomes and failed to recycle from phagosomes and cytosol to the plasma membrane. Thus, retromer is an essential mediator of apoptotic cell clearance by regulating phagocytic receptor(s) during cell corpse engulfment.

post to: CiteULike

Regulation of alternative splicing by histone modifications.

Publication Date: 2010 Feb 19 PMID: 20133523
Authors: Luco, R. F. - Pan, Q. - Tominaga, K. - Blencowe, B. J. - Pereira-Smith, O. M. - Misteli, T.
Journal: Science

Alternative splicing of pre-mRNA is a prominent mechanism to generate protein diversity, yet its regulation is poorly understood. We demonstrated a direct role for histone modifications in alternative splicing. We found distinctive histone modification signatures that correlate with the splicing outcome in a set of human genes, and modulation of histone modifications causes splice site switching. Histone marks affect splicing outcome by influencing the recruitment of splicing regulators via a chromatin-binding protein. These results outline an adaptor system for the reading of histone marks by the pre-mRNA splicing machinery.

MeSH Categories: *Alternative Splicing, Cell Line, Chromatin/metabolism, Epithelial Cells/metabolism, Exons, Histone-Lysine N-Methyltransferase/genetics/metabolism, Histones/*metabolism, Humans, Male, Mesenchymal Stem Cells/metabolism, Polypyrimidine Tract-Binding Protein/metabolism, Prostate/cytology, Protein Binding, RNA Precursors/*metabolism, Receptor, Fibroblast Growth Factor, Type 2/genetics, Transcription Factors/genetics/metabolism

post to: CiteULike

Reconstructing past seawater Mg/Ca and Sr/Ca from mid-ocean ridge flank calcium carbonate veins.

Publication Date: 2010 Feb 26 PMID: 20133522
Authors: Coggon, R. M. - Teagle, D. A. - Smith-Duque, C. E. - Alt, J. C. - Cooper, M. J.
Journal: Science

Proxies for past seawater chemistry, such as Mg/Ca and Sr/Ca ratios, provide a record of the dynamic exchanges of elements between the solid Earth, the atmosphere, and the hydrosphere and the evolving influence of life. We estimated past oceanic Mg/Ca and Sr/Ca ratios from suites of 1.6- to 170-million-year-old calcium carbonate veins that had precipitated from seawater-derived fluids in ocean ridge flank basalts. Our data indicate that before the Neogene, oceanic Mg/Ca and Sr/Ca ratios were lower than in the modern ocean. Decreased ocean spreading since the Cretaceous and the resulting slow reduction in ocean crustal hydrothermal exchange throughout the early Tertiary may explain the recent rise in these ratios.

post to: CiteULike

NMR structure determination for larger proteins using backbone-only data.

Publication Date: 2010 Feb 19 PMID: 20133520
Authors: Raman, S. - Lange, O. F. - Rossi, P. - Tyka, M. - Wang, X. - Aramini, J. - Liu, G. - Ramelot, T. A. - Eletsky, A. - Szyperski, T. - Kennedy, M. A. - Prestegard, J. - Montelione, G. T. - Baker, D.
Journal: Science

Conventional protein structure determination from nuclear magnetic resonance data relies heavily on side-chain proton-to-proton distances. The necessary side-chain resonance assignment, however, is labor intensive and prone to error. Here we show that structures can be accurately determined without nuclear magnetic resonance (NMR) information on the side chains for proteins up to 25 kilodaltons by incorporating backbone chemical shifts, residual dipolar couplings, and amide proton distances into the Rosetta protein structure modeling methodology. These data, which are too sparse for conventional methods, serve only to guide conformational search toward the lowest-energy conformations in the folding landscape; the details of the computed models are determined by the physical chemistry implicit in the Rosetta all-atom energy function. The new method is not hindered by the deuteration required to suppress nuclear relaxation processes for proteins greater than 15 kilodaltons and should enable routine NMR structure determination for larger proteins.

MeSH Categories: Computer Simulation, Models, Molecular, Monte Carlo Method, Nuclear Magnetic Resonance, Biomolecular/*methods, *Protein Conformation, Protein Folding, Proteins/*chemistry, Software, Thermodynamics

post to: CiteULike

Generating a prion with bacterially expressed recombinant prion protein.

Publication Date: 2010 Feb 26 PMID: 20110469
Authors: Wang, F. - Wang, X. - Yuan, C. G. - Ma, J.
Journal: Science

The prion hypothesis posits that a misfolded form of prion protein (PrP) is responsible for the infectivity of prion disease. Using recombinant murine PrP purified from Escherichia coli, we created a recombinant prion with the attributes of the pathogenic PrP isoform: aggregated, protease-resistant, and self-perpetuating. After intracerebral injection of the recombinant prion, wild-type mice developed neurological signs in approximately 130 days and reached the terminal stage of disease in approximately 150 days. Characterization of diseased mice revealed classic neuropathology of prion disease, the presence of protease-resistant PrP, and the capability of serially transmitting the disease; these findings confirmed that the mice succumbed to prion disease. Thus, as postulated by the prion hypothesis, the infectivity in mammalian prion disease results from an altered conformation of PrP.

post to: CiteULike

N-terminal acetylation of cellular proteins creates specific degradation signals.

Publication Date: 2010 Feb 19 PMID: 20110468
Authors: Hwang, C. S. - Shemorry, A. - Varshavsky, A.
Journal: Science

The retained N-terminal methionine (Met) residue of a nascent protein is often N-terminally acetylated (Nt-acetylated). Removal of N-terminal Met by Met-aminopeptidases frequently leads to Nt-acetylation of the resulting N-terminal alanine (Ala), valine (Val), serine (Ser), threonine (Thr), and cysteine (Cys) residues. Although a majority of eukaryotic proteins (for example, more than 80% of human proteins) are cotranslationally Nt-acetylated, the function of this extensively studied modification is largely unknown. Using the yeast Saccharomyces cerevisiae, we found that the Nt-acetylated Met residue could act as a degradation signal (degron), targeted by the Doa10 ubiquitin ligase. Moreover, Doa10 also recognized the Nt-acetylated Ala, Val, Ser, Thr, and Cys residues. Several examined proteins of diverse functions contained these N-terminal degrons, termed AcN-degrons, which are a prevalent class of degradation signals in cellular proteins.

MeSH Categories: Acetylation, Alanine/metabolism, Amino Acid Sequence, Cysteine/metabolism, Half-Life, Methionine/*metabolism, Protein Stability, Saccharomyces cerevisiae/genetics/*metabolism, Saccharomyces cerevisiae Proteins/chemistry/genetics/*metabolism, Serine/metabolism, Substrate Specificity, Ubiquitin-Protein Ligases/genetics/metabolism, Ubiquitination, Valine/metabolism

post to: CiteULike

Food security: the challenge of feeding 9 billion people.

Publication Date: 2010 Feb 12 PMID: 20110467
Authors: Godfray, H. C. - Beddington, J. R. - Crute, I. R. - Haddad, L. - Lawrence, D. - Muir, J. F. - Pretty, J. - Robinson, S. - Thomas, S. M. - Toulmin, C.
Journal: Science

Continuing population and consumption growth will mean that the global demand for food will increase for at least another 40 years. Growing competition for land, water, and energy, in addition to the overexploitation of fisheries, will affect our ability to produce food, as will the urgent requirement to reduce the impact of the food system on the environment. The effects of climate change are a further threat. But the world can produce more food and can ensure that it is used more efficiently and equitably. A multifaceted and linked global strategy is needed to ensure sustainable and equitable food security, different components of which are explored here.

MeSH Categories: *Agriculture/economics/methods/statistics & numerical data, Aquaculture, Commerce, Conservation of Natural Resources, Costs and Cost Analysis, Developed Countries, Developing Countries, Diet, *Food/economics/statistics & numerical data, Food Handling, *Food Supply/economics/statistics & numerical data, Food, Genetically Modified, Genetic Engineering, Humans, Malnutrition/epidemiology, Population Growth

post to: CiteULike

Contributions of stratospheric water vapor to decadal changes in the rate of global warming.

Publication Date: 2010 Mar 5 PMID: 20110466
Authors: Solomon, S. - Rosenlof, K. H. - Portmann, R. W. - Daniel, J. S. - Davis, S. M. - Sanford, T. J. - Plattner, G. K.
Journal: Science

Stratospheric water vapor concentrations decreased by about 10% after the year 2000. Here we show that this acted to slow the rate of increase in global surface temperature over 2000-2009 by about 25% compared to that which would have occurred due only to carbon dioxide and other greenhouse gases. More limited data suggest that stratospheric water vapor probably increased between 1980 and 2000, which would have enhanced the decadal rate of surface warming during the 1990s by about 30% as compared to estimates neglecting this change. These findings show that stratospheric water vapor is an important driver of decadal global surface climate change.

post to: CiteULike

Symmetric inertial confinement fusion implosions at ultra-high laser energies.

Publication Date: 2010 Mar 5 PMID: 20110465
Authors: Glenzer, S. H. - MacGowan, B. J. - Michel, P. - Meezan, N. B. - Suter, L. J. - Dixit, S. N. - Kline, J. L. - Kyrala, G. A. - Bradley, D. K. - Callahan, D. A. - Dewald, E. L. - Divol, L. - Dzenitis, E. - Edwards, M. J. - Hamza, A. V. - Haynam, C. A. - Hinkel, D. E. - Kalantar, D. H. - Kilkenny, J. D. - Landen, O. L. - Lindl, J. D. - LePape, S. - Moody, J. D. - Nikroo, A. - Parham, T. - Schneider, M. B. - Town, R. P. - Wegner, P. - Widmann, K. - Whitman, P. - Young, B. K. - Van Wonterghem, B. - Atherton, L. J. - Moses, E. I.
Journal: Science

Indirect-drive hohlraum experiments at the National Ignition Facility have demonstrated symmetric capsule implosions at unprecedented laser drive energies of 0.7 megajoule. One hundred and ninety-two simultaneously fired laser beams heat ignition-emulate hohlraums to radiation temperatures of 3.3 million kelvin, compressing 1.8-millimeter-diameter capsules by the soft x-rays produced by the hohlraum. Self-generated plasma optics gratings on either end of the hohlraum tune the laser power distribution in the hohlraum, which produces a symmetric x-ray drive as inferred from the shape of the capsule self-emission. These experiments indicate that the conditions are suitable for compressing deuterium-tritium-filled capsules, with the goal of achieving burning fusion plasmas and energy gain in the laboratory.

post to: CiteULike

Charged-particle probing of x-ray-driven inertial-fusion implosions.

Publication Date: 2010 Mar 5 PMID: 20110464
Authors: Li, C. K. - Seguin, F. H. - Frenje, J. A. - Rosenberg, M. - Petrasso, R. D. - Amendt, P. A. - Koch, J. A. - Landen, O. L. - Park, H. S. - Robey, H. F. - Town, R. P. - Casner, A. - Philippe, F. - Betti, R. - Knauer, J. P. - Meyerhofer, D. D. - Back, C. A. - Kilkenny, J. D. - Nikroo, A.
Journal: Science

Measurements of x-ray-driven implosions with charged particles have resulted in the quantitative characterization of critical aspects of indirect-drive inertial fusion. Three types of spontaneous electric fields differing in strength by two orders of magnitude, the largest being nearly one-tenth of the Bohr field, were discovered with time-gated proton radiographic imaging and spectrally resolved proton self-emission. The views of the spatial structure and temporal evolution of both the laser drive in a hohlraum and implosion properties provide essential insight into, and modeling validation of, x-ray-driven implosions.

post to: CiteULike

Climate-modulated channel incision and rupture history of the San Andreas Fault in the Carrizo Plain.

Publication Date: 2010 Feb 26 PMID: 20093439
Authors: Grant Ludwig, L. - Akciz, S. O. - Noriega, G. R. - Zielke, O. - Arrowsmith, J. R.
Journal: Science

The spatial and temporal distribution of fault slip is a critical parameter in earthquake source models. Previous geomorphic and geologic studies of channel offset along the Carrizo section of the south central San Andreas Fault assumed that channels form more frequently than earthquakes occur and suggested that repeated large-slip earthquakes similar to the 1857 Fort Tejon earthquake illustrate typical fault behavior. We found that offset channels in the Carrizo Plain incised less frequently than they were offset by earthquakes. Channels have been offset by successive earthquakes with variable slip since ~1400. This nonuniform slip history reveals a more complex rupture history than previously assumed for the structurally simplest section of the San Andreas Fault.

post to: CiteULike

The Lmo2 oncogene initiates leukemia in mice by inducing thymocyte self-renewal.

Publication Date: 2010 Feb 12 PMID: 20093438
Authors: McCormack, M. P. - Young, L. F. - Vasudevan, S. - de Graaf, C. A. - Codrington, R. - Rabbitts, T. H. - Jane, S. M. - Curtis, D. J.
Journal: Science

The LMO2 oncogene causes a subset of human T cell acute lymphoblastic leukemias (T-ALL), including four cases that arose as adverse events in gene therapy trials. To investigate the cellular origin of LMO2-induced leukemia, we used cell fate mapping to study mice in which the Lmo2 gene was constitutively expressed in the thymus. Lmo2 induced self-renewal of committed T cells in the mice more than 8 months before the development of overt T-ALL. These self-renewing cells retained the capacity for T cell differentiation but expressed several genes typical of hematopoietic stem cells (HSCs), suggesting that Lmo2 might reactivate an HSC-specific transcriptional program. Forced expression of one such gene, Hhex, was sufficient to initiate self-renewal of thymocytes in vivo. Thus, Lmo2 promotes the self-renewal of preleukemic thymocytes, providing a mechanism by which committed T cells can then accumulate additional genetic mutations required for leukemic transformation.

MeSH Categories: Animals, Cell Differentiation, Cell Transformation, Neoplastic/*genetics, DNA-Binding Proteins/*genetics/metabolism, Down-Regulation, Gene Expression Profiling, Gene Expression Regulation, Leukemic, Homeodomain Proteins/genetics, Humans, Metalloproteins/*genetics/metabolism, Mice, Mice, Transgenic, Oligonucleotide Array Sequence Analysis, *Oncogenes, Precursor Cells, T-Lymphoid/*physiology/transplantation, Precursor T-Cell Lymphoblastic, Leukemia-Lymphoma/*genetics/metabolism/pathology, Preleukemia/genetics/metabolism/pathology, T-Lymphocyte Subsets, T-Lymphocytes/*physiology/transplantation, Thymus Gland/metabolism/pathology, Transcription Factors/genetics, Transcription, Genetic, Up-Regulation

post to: CiteULike

Repulsion of superinfecting virions: a mechanism for rapid virus spread.

Publication Date: 2010 Feb 12 PMID: 20093437
Authors: Doceul, V. - Hollinshead, M. - van der Linden, L. - Smith, G. L.
Journal: Science

Viruses are thought to spread across susceptible cells through an iterative process of infection, replication, and release, so that the rate of spread is limited by replication kinetics. Here, we show that vaccinia virus spreads across one cell every 75 minutes, fourfold faster than its replication cycle would permit. To explain this phenomenon, we found that newly infected cells express two surface proteins that mark cells as infected and, via exploitation of cellular machinery, induce the repulsion of superinfecting virions away toward uninfected cells. Mechanistically, early expression of proteins A33 and A36 was critical for virion repulsion and rapid spread, and cells expressing these proteins repelled exogenous virions rapidly. Additional spreading mechanisms may exist for other viruses that also spread faster than predicted by replication kinetics.

MeSH Categories: Actins/metabolism, Animals, Cell Membrane/metabolism, Genes, Viral, Hela Cells, Humans, Kinetics, Membrane Glycoproteins/genetics/*metabolism, Plaque Assay, Vaccinia virus/genetics/pathogenicity/*physiology, Viral Envelope Proteins/genetics/*metabolism, Viral Structural Proteins/genetics/*metabolism, Virion/physiology, Virus Release, Virus Replication

post to: CiteULike

Slip in the 1857 and earlier large earthquakes along the Carrizo Plain, San Andreas Fault.

Publication Date: 2010 Feb 26 PMID: 20093436
Authors: Zielke, O. - Arrowsmith, J. R. - Grant Ludwig, L. - Akciz, S. O.
Journal: Science

The moment magnitude (Mw) 7.9 Fort Tejon earthquake of 1857, with a approximately 350-kilometer-long surface rupture, was the most recent major earthquake along the south-central San Andreas Fault, California. Based on previous measurements of its surface slip distribution, rupture along the approximately 60-kilometer-long Carrizo segment was thought to control the recurrence of 1857-like earthquakes. New high-resolution topographic data show that the average slip along the Carrizo segment during the 1857 event was 5.3 +/- 1.4 meters, eliminating the core assumption for a linkage between Carrizo segment rupture and recurrence of major earthquakes along the south-central San Andreas Fault. Earthquake slip along the Carrizo segment may recur in earthquake clusters with cumulative slip of approximately 5 meters.

post to: CiteULike

A genetic variant BDNF polymorphism alters extinction learning in both mouse and human.

Publication Date: 2010 Feb 12 PMID: 20075215
Authors: Soliman, F. - Glatt, C. E. - Bath, K. G. - Levita, L. - Jones, R. M. - Pattwell, S. S. - Jing, D. - Tottenham, N. - Amso, D. - Somerville, L. H. - Voss, H. U. - Glover, G. - Ballon, D. J. - Liston, C. - Teslovich, T. - Van Kempen, T. - Lee, F. S. - Casey, B. J.
Journal: Science

Mouse models are useful for studying genes involved in behavior, but whether they are relevant to human behavior is unclear. Here, we identified parallel phenotypes in mice and humans resulting from a common single-nucleotide polymorphism in the brain-derived neurotrophic factor (BDNF) gene, which is involved in anxiety-related behavior. An inbred genetic knock-in mouse strain expressing the variant BDNF recapitulated the phenotypic effects of the human polymorphism. Both were impaired in extinguishing a conditioned fear response, which was paralleled by atypical frontoamygdala activity in humans. Thus, this variant BDNF allele may play a role in anxiety disorders showing impaired learning of cues that signal safety versus threat and in the efficacy of treatments that rely on extinction mechanisms, such as exposure therapy.

MeSH Categories: Adolescent, Adult, Alleles, Amygdala/physiology, Animals, Brain Mapping, Brain-Derived Neurotrophic Factor/*genetics/*physiology, *Conditioning, Classical, Cues, Ethnic Groups/genetics, *Extinction, Psychological, *Fear, Female, Gene Knock-In Techniques, Genotype, Humans, Magnetic Resonance Imaging, Male, Mice, *Polymorphism, Single Nucleotide, Prefrontal Cortex/physiology, Young Adult

post to: CiteULike

Deglacial meltwater pulse 1B and Younger Dryas sea levels revisited with boreholes at Tahiti.

Publication Date: 2010 Mar 5 PMID: 20075212
Authors: Bard, E. - Hamelin, B. - Delanghe-Sabatier, D.
Journal: Science

Reconstructing sea-level changes during the last deglaciation provides a way of understanding the ice dynamics that can perturb large continental ice sheets. The resolution of the few sea-level records covering the critical time interval between 14,000 and 9,000 calendar years before the present is still insufficient to draw conclusions about sea-level changes associated with the Younger Dryas cold event and the meltwater pulse 1B (MWP-1B). We used the uranium-thorium method to date shallow-living corals from three new cores drilled onshore in the Tahiti barrier reef. No significant discontinuity can be detected in the sea-level rise during the MWP-1B period. The new Tahiti sea-level record shows that the sea-level rise slowed down during the Younger Dryas before accelerating again during the Holocene.

post to: CiteULike

Ferroelectric control of spin polarization.

Publication Date: 2010 Feb 26 PMID: 20075211
Authors: Garcia, V. - Bibes, M. - Bocher, L. - Valencia, S. - Kronast, F. - Crassous, A. - Moya, X. - Enouz-Vedrenne, S. - Gloter, A. - Imhoff, D. - Deranlot, C. - Mathur, N. D. - Fusil, S. - Bouzehouane, K. - Barthelemy, A.
Journal: Science

A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on "zero-current," gate-controlled operations. Efforts have been made to control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a low-power approach for spin-based information control.

post to: CiteULike

Gamma-ray emission from the shell of supernova remnant W44 revealed by the Fermi LAT.

Publication Date: 2010 Feb 26 PMID: 20056857
Authors: Abdo, A. A. - Ackermann, M. - Ajello, M. - Baldini, L. - Ballet, J. - Barbiellini, G. - Baring, M. G. - Bastieri, D. - Baughman, B. M. - Bechtol, K. - Bellazzini, R. - Berenji, B. - Blandford, R. D. - Bloom, E. D. - Bonamente, E. - Borgland, A. W. - Bregeon, J. - Brez, A. - Brigida, M. - Bruel, P. - Burnett, T. H. - Buson, S. - Caliandro, G. A. - Cameron, R. A. - Caraveo, P. A. - Casandjian, J. M. - Cecchi, C. - Celik, O. - Chekhtman, A. - Cheung, C. C. - Chiang, J. - Ciprini, S. - Claus, R. - Cognard, I. - Cohen-Tanugi, J. - Cominsky, L. R. - Conrad, J. - Cutini, S. - Dermer, C. D. - de Angelis, A. - de Palma, F. - Digel, S. W. - do Couto e Silva, E. - Drell, P. S. - Dubois, R. - Dumora, D. - Espinoza, C. - Farnier, C. - Favuzzi, C. - Fegan, S. J. - Focke, W. B. - Fortin, P. - Frailis, M. - Fukazawa, Y. - Funk, S. - Fusco, P. - Gargano, F. - Gasparrini, D. - Gehrels, N. - Germani, S. - Giavitto, G. - Giebels, B. - Giglietto, N. - Giordano, F. - Glanzman, T. - Godfrey, G. - Grenier, I. A. - Grondin, M. H. - Grove, J. E. - Guillemot, L. - Guiriec, S. - Hanabata, Y. - Harding, A. K. - Hayashida, M. - Hays, E. - Hughes, R. E. - Jackson, M. S. - Johannesson, G. - Johnson, A. S. - Johnson, T. J. - Johnson, W. N. - Kamae, T. - Katagiri, H. - Kataoka, J. - Katsuta, J. - Kawai, N. - Kerr, M. - Knodlseder, J. - Kocian, M. L. - Kramer, M. - Kuss, M. - Lande, J. - Latronico, L. - Lemoine-Goumard, M. - Longo, F. - Loparco, F. - Lott, B. - Lovellette, M. N. - Lubrano, P. - Lyne, A. G. - Madejski, G. M. - Makeev, A. - Mazziotta, M. N. - McEnery, J. E. - Meurer, C. - Michelson, P. F. - Mitthumsiri, W. - Mizuno, T. - Monte, C. - Monzani, M. E. - Morselli, A. - Moskalenko, I. V. - Murgia, S. - Nakamori, T. - Nolan, P. L. - Norris, J. P. - Noutsos, A. - Nuss, E. - Ohsugi, T. - Omodei, N. - Orlando, E. - Ormes, J. F. - Paneque, D. - Parent, D. - Pelassa, V. - Pepe, M. - Pesce-Rollins, M. - Piron, F. - Porter, T. A. - Raino, S. - Rando, R. - Razzano, M. - Reimer, A. - Reimer, O. - Reposeur, T. - Rochester, L. S. - Rodriguez, A. Y. - Romani, R. W. - Roth, M. - Ryde, F. - Sadrozinski, H. F. - Sanchez, D. - Sander, A. - Saz Parkinson, P. M. - Scargle, J. D. - Sgro, C. - Siskind, E. J. - Smith, D. A. - Smith, P. D. - Spandre, G. - Spinelli, P. - Stappers, B. W. - Stecker, F. W. - Strickman, M. S. - Suson, D. J. - Tajima, H. - Takahashi, H. - Takahashi, T. - Tanaka, T. - Thayer, J. B. - Thayer, J. G. - Theureau, G. - Thompson, D. J. - Tibaldo, L. - Tibolla, O. - Torres, D. F. - Tosti, G. - Tramacere, A. - Uchiyama, Y. - Usher, T. L. - Vasileiou, V. - Venter, C. - Vilchez, N. - Vitale, V. - Waite, A. P. - Wang, P. - Winer, B. L. - Wood, K. S. - Yamazaki, R. - Ylinen, T. - Ziegler, M.
Journal: Science

Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to ~10(15) electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 x 10(8) electron volts and 3 x10(11) electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above approximately 10(9) electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.

post to: CiteULike

Kepler planet-detection mission: introduction and first results.

Publication Date: 2010 Feb 19 PMID: 20056856
Authors: Borucki, W. J. - Koch, D. - Basri, G. - Batalha, N. - Brown, T. - Caldwell, D. - Caldwell, J. - Christensen-Dalsgaard, J. - Cochran, W. D. - DeVore, E. - Dunham, E. W. - Dupree, A. K. - Gautier, T. N. 3rd - Geary, J. C. - Gilliland, R. - Gould, A. - Howell, S. B. - Jenkins, J. M. - Kondo, Y. - Latham, D. W. - Marcy, G. W. - Meibom, S. - Kjeldsen, H. - Lissauer, J. J. - Monet, D. G. - Morrison, D. - Sasselov, D. - Tarter, J. - Boss, A. - Brownlee, D. - Owen, T. - Buzasi, D. - Charbonneau, D. - Doyle, L. - Fortney, J. - Ford, E. B. - Holman, M. J. - Seager, S. - Steffen, J. H. - Welsh, W. F. - Rowe, J. - Anderson, H. - Buchhave, L. - Ciardi, D. - Walkowicz, L. - Sherry, W. - Horch, E. - Isaacson, H. - Everett, M. E. - Fischer, D. - Torres, G. - Johnson, J. A. - Endl, M. - MacQueen, P. - Bryson, S. T. - Dotson, J. - Haas, M. - Kolodziejczak, J. - Van Cleve, J. - Chandrasekaran, H. - Twicken, J. D. - Quintana, E. V. - Clarke, B. D. - Allen, C. - Li, J. - Wu, H. - Tenenbaum, P. - Verner, E. - Bruhweiler, F. - Barnes, J. - Prsa, A.
Journal: Science

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (approximately 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.

post to: CiteULike

A composite of multiple signals distinguishes causal variants in regions of positive selection.

Publication Date: 2010 Feb 12 PMID: 20056855
Authors: Grossman, S. R. - Shylakhter, I. - Karlsson, E. K. - Byrne, E. H. - Morales, S. - Frieden, G. - Hostetter, E. - Angelino, E. - Garber, M. - Zuk, O. - Lander, E. S. - Schaffner, S. F. - Sabeti, P. C.
Journal: Science

The human genome contains hundreds of regions whose patterns of genetic variation indicate recent positive natural selection, yet for most the underlying gene and the advantageous mutation remain unknown. We developed a method, composite of multiple signals (CMS), that combines tests for multiple signals of selection and increases resolution by up to 100-fold. By applying CMS to candidate regions from the International Haplotype Map, we localized population-specific selective signals to 55 kilobases (median), identifying known and novel causal variants. CMS can not just identify individual loci but implicates precise variants selected by evolution.

MeSH Categories: Computational Biology/methods, DNA, Intergenic/genetics, Evolution, Molecular, Genetic Loci, *Genetic Variation, *Genome, Human, Haplotypes, Humans, Polymorphism, Genetic, Population Groups/genetics, Regulatory Sequences, Nucleic Acid/genetics, *Selection, Genetic, Software

post to: CiteULike

Darwinian evolution of prions in cell culture.

Publication Date: 2010 Feb 12 PMID: 20044542
Authors: Li, J. - Browning, S. - Mahal, S. P. - Oelschlegel, A. M. - Weissmann, C.
Journal: Science

Prions are infectious proteins consisting mainly of PrP(Sc), a beta sheet-rich conformer of the normal host protein PrP(C), and occur in different strains. Strain identity is thought to be encoded by PrP(Sc) conformation. We found that biologically cloned prion populations gradually became heterogeneous by accumulating "mutants," and selective pressures resulted in the emergence of different mutants as major constituents of the evolving population. Thus, when transferred from brain to cultured cells, "cell-adapted" prions outcompeted their "brain-adapted" counterparts, and the opposite occurred when prions were returned from cells to brain. Similarly, the inhibitor swainsonine selected for a resistant substrain, whereas, in its absence, the susceptible substrain outgrew its resistant counterpart. Prions, albeit devoid of a nucleic acid genome, are thus subject to mutation and selective amplification.

MeSH Categories: Animals, *Brain Chemistry, Cell Line, Cell Line, Tumor, Culture Media, Culture Media, Conditioned, *Evolution, Molecular, Mice, Mice, Inbred C57BL, Mutation, *PrPSc Proteins/chemistry/classification/pathogenicity, Prion Diseases, Prions/chemistry/classification/*pathogenicity/*physiology, Protein Conformation, Swainsonine/pharmacology

post to: CiteULike

Drive against hotspot motifs in primates implicates the PRDM9 gene in meiotic recombination.

Publication Date: 2010 Feb 12 PMID: 20044541
Authors: Myers, S. - Bowden, R. - Tumian, A. - Bontrop, R. E. - Freeman, C. - MacFie, T. S. - McVean, G. - Donnelly, P.
Journal: Science

Although present in both humans and chimpanzees, recombination hotspots, at which meiotic crossover events cluster, differ markedly in their genomic location between the species. We report that a 13-base pair sequence motif previously associated with the activity of 40% of human hotspots does not function in chimpanzees and is being removed by self-destructive drive in the human lineage. Multiple lines of evidence suggest that the rapidly evolving zinc-finger protein PRDM9 binds to this motif and that sequence changes in the protein may be responsible for hotspot differences between species. The involvement of PRDM9, which causes histone H3 lysine 4 trimethylation, implies that there is a common mechanism for recombination hotspots in eukaryotes but raises questions about what forces have driven such rapid change.

MeSH Categories: Animals, Base Sequence, Crossing Over, Genetic, DNA/metabolism, Evolution, Molecular, Histone-Lysine N-Methyltransferase/chemistry/*genetics/metabolism, Histones/metabolism, Humans, Meiosis/*genetics, Methylation, Pan troglodytes/*genetics, Polymorphism, Single Nucleotide, *Recombination, Genetic, Species Specificity

post to: CiteULike

PRDM9 is a major determinant of meiotic recombination hotspots in humans and mice.

Publication Date: 2010 Feb 12 PMID: 20044539
Authors: Baudat, F. - Buard, J. - Grey, C. - Fledel-Alon, A. - Ober, C. - Przeworski, M. - Coop, G. - de Massy, B.
Journal: Science

Meiotic recombination events cluster into narrow segments of the genome, defined as hotspots. Here, we demonstrate that a major player for hotspot specification is the Prdm9 gene. First, two mouse strains that differ in hotspot usage are polymorphic for the zinc finger DNA binding array of PRDM9. Second, the human consensus PRDM9 allele is predicted to recognize the 13-mer motif enriched at human hotspots; this DNA binding specificity is verified by in vitro studies. Third, allelic variants of PRDM9 zinc fingers are significantly associated with variability in genome-wide hotspot usage among humans. Our results provide a molecular basis for the distribution of meiotic recombination in mammals, in which the binding of PRDM9 to specific DNA sequences targets the initiation of recombination at specific locations in the genome.

MeSH Categories: Alleles, Amino Acid Sequence, Animals, Base Sequence, Binding Sites, DNA/chemistry/metabolism, DNA Breaks, Double-Stranded, DNA-Binding Proteins/chemistry/genetics/metabolism, Genome, Genome, Human, Genotype, Histone-Lysine N-Methyltransferase/chemistry/*genetics/*metabolism, Humans, Meiosis/*genetics, Mice, Mice, Inbred C57BL, Molecular Sequence Data, Phenotype, *Recombination, Genetic, Zinc Fingers/genetics

post to: CiteULike

Prdm9 controls activation of mammalian recombination hotspots.

Publication Date: 2010 Feb 12 PMID: 20044538
Authors: Parvanov, E. D. - Petkov, P. M. - Paigen, K.
Journal: Science

Mammalian meiotic recombination, which preferentially occurs at specialized sites called hotspots, ensures the orderly segregation of meiotic chromosomes and creates genetic variation among offspring. A locus on mouse chromosome 17, which controls activation of recombination at multiple distant hotspots, has been mapped within a 181-kilobase interval, three of whose genes can be eliminated as candidates. The remaining gene, Prdm9, codes for a zinc finger containing histone H3K4 trimethylase that is expressed in early meiosis and whose deficiency results in sterility in both sexes. Mus musculus exhibits five alleles of Prdm9; human populations exhibit two predominant alleles and multiple minor alleles. The identification of Prdm9 as a protein regulating mammalian recombination hotspots initiates molecular studies of this important biological control system.

MeSH Categories: Alleles, Amino Acid Sequence, Animals, Chromosome Mapping, Female, Histone-Lysine N-Methyltransferase/chemistry/*genetics/metabolism, Humans, Male, Meiosis/*genetics, Mice, Mice, Inbred C57BL, Molecular Sequence Data, *Recombination, Genetic, Sequence Analysis, DNA, Testis/metabolism, Zinc Fingers

post to: CiteULike