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排序方式: 共有1972条查询结果,搜索用时 15 毫秒
941.
Chisholm MF Wang Y Lupini AR Eres G Puretzky AA Brinson B Melechko AV Geohegan DB Cui H Johnson MP Pennycook SJ Lowndes DH Arepalli S Kittrell C Sivaram S Kim M Lavin G Kono J Hauge R Smalley RE 《Science (New York, N.Y.)》2003,300(5623):1236; author reply 1236
942.
Greenbaum DC Baruch A Grainger M Bozdech Z Medzihradszky KF Engel J DeRisi J Holder AA Bogyo M 《Science (New York, N.Y.)》2002,298(5600):2002-2006
Cysteine proteases of Plasmodium falciparum are required for survival of the malaria parasite, yet their specific cellular functions remain unclear. We used a chemical proteomic screen with a small-molecule probe to characterize the predominant cysteine proteases throughout the parasite life cycle. Only one protease, falcipain 1, was active during the invasive merozoite stage. Falcipain 1-specific inhibitors, identified by screening of chemical libraries, blocked parasite invasion of host erythrocytes, yet had no effect on normal parasite processes such as hemoglobin degradation. These results demonstrate a specific role for falcipain 1 in host cell invasion and establish a potential new target for antimalarial therapeutics. 相似文献
943.
Gardner MJ Bishop R Shah T de Villiers EP Carlton JM Hall N Ren Q Paulsen IT Pain A Berriman M Wilson RJ Sato S Ralph SA Mann DJ Xiong Z Shallom SJ Weidman J Jiang L Lynn J Weaver B Shoaibi A Domingo AR Wasawo D Crabtree J Wortman JR Haas B Angiuoli SV Creasy TH Lu C Suh B Silva JC Utterback TR Feldblyum TV Pertea M Allen J Nierman WC Taracha EL Salzberg SL White OR Fitzhugh HA Morzaria S Venter JC Fraser CM Nene V 《Science (New York, N.Y.)》2005,309(5731):134-137
We report the genome sequence of Theileria parva, an apicomplexan pathogen causing economic losses to smallholder farmers in Africa. The parasite chromosomes exhibit limited conservation of gene synteny with Plasmodium falciparum, and its plastid-like genome represents the first example where all apicoplast genes are encoded on one DNA strand. We tentatively identify proteins that facilitate parasite segregation during host cell cytokinesis and contribute to persistent infection of transformed host cells. Several biosynthetic pathways are incomplete or absent, suggesting substantial metabolic dependence on the host cell. One protein family that may generate parasite antigenic diversity is not telomere-associated. 相似文献
944.
Deformation of metals and alloys by dislocations gliding between well-separated slip planes is a well-understood process, but most crystal structures do not possess such simple geometric arrangements. Examples are the Laves phases, the most common class of intermetallic compounds and exist with ordered cubic, hexagonal, and rhombohedral structures. These compounds are usually brittle at low temperatures, and transformation from one structure to another is slow. On the basis of geometric and energetic considerations, a dislocation-based mechanism consisting of two shears in different directions on adjacent atomic planes has been used to explain both deformation and phase transformations in this class of materials. We report direct observations made by Z-contrast atomic resolution microscopy of stacking faults and dislocation cores in the Laves phase Cr2Hf. These results show that this complex dislocation scheme does indeed operate in this material. Knowledge gained of the dislocation core structure will enable improved understanding of deformation mechanisms and phase transformation kinetics in this and other complex structures. 相似文献
945.
Hoover K Grove M Gardner M Hughes DP McNeil J Slavicek J 《Science (New York, N.Y.)》2011,333(6048):1401
Manipulation of host behavior by parasites and pathogens has been widely observed, but the basis for these behaviors has remained elusive. Gypsy moths infected by a baculovirus climb to the top of trees to die, liquefy, and "rain" virus on the foliage below to infect new hosts. The viral gene that manipulates climbing behavior of the host was identified, providing evidence of a genetic basis for the extended phenotype. 相似文献
946.
The structure of haplotype blocks in the human genome 总被引:1,自引:0,他引:1
Gabriel SB Schaffner SF Nguyen H Moore JM Roy J Blumenstiel B Higgins J DeFelice M Lochner A Faggart M Liu-Cordero SN Rotimi C Adeyemo A Cooper R Ward R Lander ES Daly MJ Altshuler D 《Science (New York, N.Y.)》2002,296(5576):2225-2229
Haplotype-based methods offer a powerful approach to disease gene mapping, based on the association between causal mutations and the ancestral haplotypes on which they arose. As part of The SNP Consortium Allele Frequency Projects, we characterized haplotype patterns across 51 autosomal regions (spanning 13 megabases of the human genome) in samples from Africa, Europe, and Asia. We show that the human genome can be parsed objectively into haplotype blocks: sizable regions over which there is little evidence for historical recombination and within which only a few common haplotypes are observed. The boundaries of blocks and specific haplotypes they contain are highly correlated across populations. We demonstrate that such haplotype frameworks provide substantial statistical power in association studies of common genetic variation across each region. Our results provide a foundation for the construction of a haplotype map of the human genome, facilitating comprehensive genetic association studies of human disease. 相似文献
947.
Enols are common intermediates in hydrocarbon oxidation 总被引:1,自引:0,他引:1
Taatjes CA Hansen N McIlroy A Miller JA Senosiain JP Klippenstein SJ Qi F Sheng L Zhang Y Cool TA Wang J Westmoreland PR Law ME Kasper T Kohse-Höinghaus K 《Science (New York, N.Y.)》2005,308(5730):1887-1889
Models for chemical mechanisms of hydrocarbon oxidation rely on spectrometric identification of molecular structures in flames. Carbonyl (keto) compounds are well-established combustion intermediates. However, their less-stable enol tautomers, bearing OH groups adjacent to carbon-carbon double bonds, are not included in standard models. We observed substantial quantities of two-, three-, and four-carbon enols by photoionization mass spectrometry of flames burning representative compounds from modern fuel blends. Concentration profiles demonstrate that enol flame chemistry cannot be accounted for purely by keto-enol tautomerization. Currently accepted hydrocarbon oxidation mechanisms will likely require revision to explain the formation and reactivity of these unexpected compounds. 相似文献
948.
Yarovinsky F Zhang D Andersen JF Bannenberg GL Serhan CN Hayden MS Hieny S Sutterwala FS Flavell RA Ghosh S Sher A 《Science (New York, N.Y.)》2005,308(5728):1626-1629
Mammalian Toll-like receptors (TLRs) play an important role in the innate recognition of pathogens by dendritic cells (DCs). Although TLRs are clearly involved in the detection of bacteria and viruses, relatively little is known about their function in the innate response to eukaryotic microorganisms. Here we identify a profilin-like molecule from the protozoan parasite Toxoplasma gondii that generates a potent interleukin-12 (IL-12) response in murine DCs that is dependent on myeloid differentiation factor 88. T. gondii profilin activates DCs through TLR11 and is the first chemically defined ligand for this TLR. Moreover, TLR11 is required in vivo for parasite-induced IL-12 production and optimal resistance to infection, thereby establishing a role for the receptor in host recognition of protozoan pathogens. 相似文献
949.
Kelley DS Karson JA Früh-Green GL Yoerger DR Shank TM Butterfield DA Hayes JM Schrenk MO Olson EJ Proskurowski G Jakuba M Bradley A Larson B Ludwig K Glickson D Buckman K Bradley AS Brazelton WJ Roe K Elend MJ Delacour A Bernasconi SM Lilley MD Baross JA Summons RE Sylva SP 《Science (New York, N.Y.)》2005,307(5714):1428-1434
The serpentinite-hosted Lost City hydrothermal field is a remarkable submarine ecosystem in which geological, chemical, and biological processes are intimately interlinked. Reactions between seawater and upper mantle peridotite produce methane- and hydrogen-rich fluids, with temperatures ranging from <40 degrees to 90 degrees C at pH 9 to 11, and carbonate chimneys 30 to 60 meters tall. A low diversity of microorganisms related to methane-cycling Archaea thrive in the warm porous interiors of the edifices. Macrofaunal communities show a degree of species diversity at least as high as that of black smoker vent sites along the Mid-Atlantic Ridge, but they lack the high biomasses of chemosynthetic organisms that are typical of volcanically driven systems. 相似文献
950.