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排序方式: 共有229条查询结果,搜索用时 15 毫秒
221.
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Smeulders MJ Barends TR Pol A Scherer A Zandvoort MH Udvarhelyi A Khadem AF Menzel A Hermans J Shoeman RL Wessels HJ van den Heuvel LP Russ L Schlichting I Jetten MS Op den Camp HJ 《Nature》2011,478(7369):412-416
Extremophilic organisms require specialized enzymes for their exotic metabolisms. Acid-loving thermophilic Archaea that live in the mudpots of volcanic solfataras obtain their energy from reduced sulphur compounds such as hydrogen sulphide (H(2)S) and carbon disulphide (CS(2)). The oxidation of these compounds into sulphuric acid creates the extremely acidic environment that characterizes solfataras. The hyperthermophilic Acidianus strain A1-3, which was isolated from the fumarolic, ancient sauna building at the Solfatara volcano (Naples, Italy), was shown to rapidly convert CS(2) into H(2)S and carbon dioxide (CO(2)), but nothing has been known about the modes of action and the evolution of the enzyme(s) involved. Here we describe the structure, the proposed mechanism and evolution of a CS(2) hydrolase from Acidianus A1-3. The enzyme monomer displays a typical β-carbonic anhydrase fold and active site, yet CO(2) is not one of its substrates. Owing to large carboxy- and amino-terminal arms, an unusual hexadecameric catenane oligomer has evolved. This structure results in the blocking of the entrance to the active site that is found in canonical β-carbonic anhydrases and the formation of a single 15-?-long, highly hydrophobic tunnel that functions as a specificity filter. The tunnel determines the enzyme's substrate specificity for CS(2), which is hydrophobic. The transposon sequences that surround the gene encoding this CS(2) hydrolase point to horizontal gene transfer as a mechanism for its acquisition during evolution. Our results show how the ancient β-carbonic anhydrase, which is central to global carbon metabolism, was transformed by divergent evolution into a crucial enzyme in CS(2) metabolism. 相似文献
223.
Yu Liu CaiYong Wang WenJun Hao HuiMing Song QiuFang Cai Hua Tian Bo Sun Hans W. Linderholm 《科学通报(英文版)》2011,56(28-29):2995-3002
A tree-ring-width chronology of Pinus tabulaeformis from Kalaqin, Inner Mongolia was developed using modern dendrochronological techniques. Based on the results of correlation function analysis, the total precipitation from the previous August to current July was reconstructed for 1771?C2008 AD with an explained variance of 49.3%. The reconstruction correlated well with the dryness/wetness series derived from historical documents, as well as the precipitation reconstruction of the Chifeng-Weichang region. There were eight intervals with greater precipitation than the average (associated with the strong East Asian summer monsoon) and seven intervals lower than the average (weak monsoon). A power spectrum analysis showed that there were 120 a, 80 a, 8 a and 2 a periodicities. 相似文献
224.
Specificity in Toll-like receptor signalling through distinct effector functions of TRAF3 and TRAF6 总被引:1,自引:0,他引:1
Häcker H Redecke V Blagoev B Kratchmarova I Hsu LC Wang GG Kamps MP Raz E Wagner H Häcker G Mann M Karin M 《Nature》2006,439(7073):204-207
Toll-like receptors (TLRs) are activated by pathogen-associated molecular patterns to induce innate immune responses and production of pro-inflammatory cytokines, interferons and anti-inflammatory cytokines. TLRs activate downstream effectors through adaptors that contain Toll/interleukin-1 receptor (TIR) domains, but the mechanisms accounting for diversification of TLR effector functions are unclear. To dissect biochemically TLR signalling, we established a system for isolating signalling complexes assembled by dimerized adaptors. Using MyD88 as a prototypical adaptor, we identified TNF receptor-associated factor 3 (TRAF3) as a new component of TIR signalling complexes that is recruited along with TRAF6. Using myeloid cells from TRAF3- and TRAF6-deficient mice, we show that TRAF3 is essential for the induction of type I interferons (IFN) and the anti-inflammatory cytokine interleukin-10 (IL-10), but is dispensable for expression of pro-inflammatory cytokines. In fact, TRAF3-deficient cells overproduce pro-inflammatory cytokines owing to defective IL-10 production. Despite their structural similarity, the functions of TRAF3 and TRAF6 are largely distinct. TRAF3 is also recruited to the adaptor TRIF (Toll/IL-1 receptor domain-containing adaptor-inducing IFN-beta) and is required for marshalling the protein kinase TBK1 (also called NAK) into TIR signalling complexes, thereby explaining its unique role in activation of the IFN response. 相似文献
225.
Hans C. Ohanian 《Studies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics》2012,43(3):215-217
N. D. Mermin has proposed an “elaboration” of Einstein's 1905 derivation that supposedly fixes the flaws that I identified in this derivation. By specific examples taken from Einstein's own later work, I show that Mermin's elaboration is fraught with misconceptions. 相似文献
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227.
Ohne Zusammenfassung 相似文献
228.
Hans Hurni 《Cellular and molecular life sciences : CMLS》1946,2(2):66-67
Summary In case ofAbsidia coerulea, Mucor mucedo, Rhizopus nodosus, Rhizopus oryzae andRhizopus suinus (auxoautotroph), Hypoxanthine effects, as well as in case ofPhycomyces Blakesleeanus (auxo-heterotroph), by acceleration of the germinating of the spores a temporary increased growth in contrary to controls without this additional growth factor. 相似文献
229.