RECENT PROGRESS IN SOLAR PHYSICS AS BEARING UPON THE CAUSE OF THE ICE AGE     

Bishop SE 《Science (New York, N.Y.)》1891,17(430):239-241

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Atmospheric and Seismic Influences     

Bishop SE 《Science (New York, N.Y.)》1891,18(441):39-40

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The "sunday seminar"     

Ptashne M  Gilbert W  Baltimore D  Gefter M  Steitz J  Bishop M  Guthrie C  Boyer H  Sobell H  Abelson J  Alberts B 《Science (New York, N.Y.)》1976,191(4224):245

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Energetics of hydrogen bond network rearrangements in liquid water     

Smith JD  Cappa CD  Wilson KR  Messer BM  Cohen RC  Saykally RJ 《Science (New York, N.Y.)》2004,306(5697):851-853

A strong temperature dependence of oxygen K-edge x-ray absorption fine structure features was observed for supercooled and normal liquid water droplets prepared from the breakup of a liquid microjet. Analysis of the data over the temperature range 251 to 288 kelvin (-22 degrees to +15 degrees C) yields a value of 1.5 +/- 0.5 kilocalories per mole for the average thermal energy required to effect an observable rearrangement between the fully coordinated ("ice-like") and distorted ("broken-donor") local hydrogen-bonding configurations responsible for the pre-edge and post-edge features, respectively. This energy equals the latent heat of melting of ice with hexagonal symmetry (ice Ih) and is consistent with the distribution of hydrogen bond strengths obtained for the "overstructured" ST2 model of water.  相似文献   

Mechanism of Na+/H+ antiporting     

Arkin IT  Xu H  Jensen MØ  Arbely E  Bennett ER  Bowers KJ  Chow E  Dror RO  Eastwood MP  Flitman-Tene R  Gregersen BA  Klepeis JL  Kolossváry I  Shan Y  Shaw DE 《Science (New York, N.Y.)》2007,317(5839):799-803

Na+/H+ antiporters are central to cellular salt and pH homeostasis. The structure of Escherichia coli NhaA was recently determined, but its mechanisms of transport and pH regulation remain elusive. We performed molecular dynamics simulations of NhaA that, with existing experimental data, enabled us to propose an atomically detailed model of antiporter function. Three conserved aspartates are key to our proposed mechanism: Asp164 (D164) is the Na+-binding site, D163 controls the alternating accessibility of this binding site to the cytoplasm or periplasm, and D133 is crucial for pH regulation. Consistent with experimental stoichiometry, two protons are required to transport a single Na+ ion: D163 protonates to reveal the Na+-binding site to the periplasm, and subsequent protonation of D164 releases Na+. Additional mutagenesis experiments further validated the model.  相似文献   

Glacial research. Melting glaciers release ancient relics     

Krajick K 《Science (New York, N.Y.)》2002,296(5567):454-456

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Melanin,nutrition, and the lion's mane     

Hill GE  McGraw KJ 《Science (New York, N.Y.)》2003,299(5607):660; author reply 660

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Structural basis of a phototropin light switch     

Harper SM  Neil LC  Gardner KH 《Science (New York, N.Y.)》2003,301(5639):1541-1544

Phototropins are light-activated kinases important for plant responses to blue light. Light initiates signaling in these proteins by generating a covalent protein-flavin mononucleotide (FMN) adduct within sensory Per-ARNT-Sim (PAS) domains. We characterized the light-dependent changes of a phototropin PAS domain by solution nuclear magnetic resonance spectroscopy and found that an alpha helix located outside the canonical domain plays a key role in this activation process. Although this helix associates with the PAS core in the dark, photoinduced changes in the domain structure disrupt this interaction. We propose that this mechanism couples light-dependent bond formation to kinase activation and identifies a signaling pathway conserved among PAS domains.  相似文献   

Ecology. Winning the war against island invaders     

Krajick K 《Science (New York, N.Y.)》2005,310(5753):1410-1413

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Cell biology. Ancient neurons regulate immunity     

Tracey KJ 《Science (New York, N.Y.)》2011,332(6030):673-674

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