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排序方式： 共有1938条查询结果，搜索用时 46 毫秒
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Culliton BJ 《Science (New York, N.Y.)》1976,193(4250):300-301
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Casassus B 《Science (New York, N.Y.)》2003,299(5614):1823-1824
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The mammalian intestine harbors a beneficial microbiota numbering approximately 10(12) organisms per gram of colonic content. The host tolerates this tremendous bacterial load while maintaining the ability to efficiently respond to pathogenic organisms. In this study, we show that the Bacteroides use a mammalian-like pathway to decorate numerous surface capsular polysaccharides and glycoproteins with l-fucose, an abundant surface molecule of intestinal epithelial cells, resulting in the coordinated expression of this surface molecule by host and symbiont. A Bacteroides mutant deficient in the ability to cover its surface with L-fucose is defective in colonizing the mammalian intestine under competitive conditions. 相似文献
128.
Solutes have been added to strengthen elemental metals, generating usable materials for millennia; in the 1960s, solutes were found to also soften metals. Despite the empirical correlation between the "electron number" of the solute and the change in strength of the material to which it is added, the mechanism responsible for softening is poorly understood. Using state-of-the-art quantum-mechanical methods, we studied the direct interaction of transition-metal solutes with dislocations in molybdenum. The interaction increases dramatically with increasing electron number and strongly influences the mechanisms responsible for plasticity in these materials. Our quantitative model explains solution softening of metals by using changes in energy and stress scales of plasticity from solutes. 相似文献
129.
Two isoacceptor transfer RNA's for lysine were found in rabbit reticulocytes. The codon recognition properties of these isoacceptors were studied in hemoglobin synthesis in a cell-free systemn. The two isoacceptors transferred lysine into different sites in hemoglobin, but showed no preference for one chain over the other. Codon cross recognition was less than 4 percent. 相似文献
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Culliton BJ 《Science (New York, N.Y.)》1975,190(4221):1271-1275