全文获取类型
收费全文 | 488篇 |
免费 | 70篇 |
国内免费 | 1篇 |
专业分类
559篇 |
出版年
2018年 | 6篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 17篇 |
2014年 | 17篇 |
2013年 | 13篇 |
2012年 | 25篇 |
2011年 | 23篇 |
2010年 | 16篇 |
2009年 | 22篇 |
2008年 | 20篇 |
2007年 | 17篇 |
2006年 | 14篇 |
2005年 | 17篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 10篇 |
2000年 | 18篇 |
1999年 | 14篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1994年 | 3篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 19篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 11篇 |
1976年 | 5篇 |
1975年 | 8篇 |
1974年 | 10篇 |
1972年 | 7篇 |
1970年 | 3篇 |
1969年 | 5篇 |
1968年 | 6篇 |
1967年 | 6篇 |
1966年 | 4篇 |
1965年 | 4篇 |
排序方式: 共有559条查询结果,搜索用时 0 毫秒
131.
132.
Crystal structure of the lysine-, arginine-, ornithine-binding protein (LAO) from Salmonella typhimurium at 2.7-A resolution. 总被引:11,自引:0,他引:11
C H Kang W C Shin Y Yamagata S Gokcen G F Ames S H Kim 《The Journal of biological chemistry》1991,266(35):23893-23899
A wide variety of sugars, amino acids, peptides, and inorganic ions are transported into bacteria by periplasmic transport systems consisting of substrate-specific receptors (binding proteins) and membrane-bound protein complexes. The crystal structure of the lysine-, arginine-, ornithine-binding protein (LAO) at 2.7-A resolution shows that the molecule has a bi-lobal structure and that its topological structure is different from other amino acid-binding proteins but is similar to the sulfate-binding protein and maltose-binding protein. High sequence homology between LAO and the histidine-binding protein (HisJ) and the fact that LAO and HisJ share the same membrane-bound protein complex allow one to define functional regions responsible for the ligand binding and for the interaction with the membrane complex. 相似文献
133.
The membrane-bound proteins of periplasmic permeases form a complex. Identification of the histidine permease HisQMP complex 总被引:19,自引:0,他引:19
R E Kerppola V K Shyamala P Klebba G F Ames 《The Journal of biological chemistry》1991,266(15):9857-9865
The membrane-bound proteins of periplasmic transport systems have been hypothesized to form a complex with relatively little experimental support. Here we present experimental evidence that HisQ, HisM, and HisP, the membrane-bound proteins of the periplasmic histidine transport system of Salmonella typhimurium, form such a complex. We have developed antibodies specific to each of these proteins to aid in their characterization. Extractions with urea, alkaline pH, or Triton X-114 show that HisQ and HisM are integral membrane proteins. By these tests HisP displays an unusual behavior, being associated with the membrane whether or not HisQ and HisM are present and despite its hydrophilic sequence. However, the nature of HisPs interaction with the membrane is shown to vary depending on the presence of HisQ and HisM. In their absence, HisP is somewhat peripherally associated with the membrane, while in their presence it binds much more tightly, indicating that it forms a complex in association with HisQ and HisM. This is demonstrated by the coimmunoprecipitation of all three proteins by antibodies directed against any one of them. Chemical cross-linking allowed the characterization of the subunit stoichiometry of the complex as two HisPs to one HisQ and one HisM. Within this complex all three proteins probably contact each other and the two HisPs form a dimer. We hypothesize that HisQ and HisM with their multiple membrane-spanning segments form a "channel" within which the HisP subunits are located. 相似文献
134.
Simple, rapid, and quantitative release of periplasmic proteins by chloroform. 总被引:54,自引:29,他引:25 下载免费PDF全文
We introduce a method by which periplasmic proteins can be released rapidly, simply, and quantitatively by treating cells with chloroform. All the amino acid-binding proteins tested maintained their activity during chloroform treatment. This method makes practical the analysis of the periplasmic protein complement of a large number of strains. 相似文献
135.
J R Ames U Hollstein A R Gagneux M D Ryan P Kovacic 《Free radical biology & medicine》1987,3(2):85-96
Cyclic voltammetry data were obtained for most of the main categories of antiamebic agents, specifically, quinones, heterocyclic nitro compounds, metal derivatives and chelators, and iminium-type ions. The reductions (our data and literature values) were for the most part reversible, with potentials usually in the favorable range of +0.10 to -0.56 V. The drug effect is believed to result generally from the catalytic production of oxidative stress usually arising from the formation of superoxide via electron transfer. In addition, relevant literature data are provided. 相似文献
136.
E Prossnitz K Nikaido S J Ulbrich G F Ames 《The Journal of biological chemistry》1988,263(34):17917-17920
The histidine permease of Salmonella typhimurium consists of four protein components, one located in the periplasm and three in the cytoplasmic membrane. Genetic evidence indicated that the periplasmic protein interacts with the membrane proteins during transport. We have utilized two different methods to demonstrate that the periplasmic protein cross-links specifically to one of the membrane components, the Q protein. Formaldehyde, a water-soluble permeant molecule was used in vivo. Sulfosuccinimidyl 6-(4'-azido-2'-nitrophenylamino)hexanoate, a photoactivatable cross-linking reagent, was used in vitro in a reconstituted membrane vesicle system. Furthermore, we show that a mutant periplasmic protein, capable of binding substrate but not transporting it, is defective in cross-linking to the membrane protein, indicating this interaction to be a crucial step in the mechanism of transport. 相似文献
137.
Energy coupling in bacterial periplasmic transport systems. Studies in intact Escherichia coli cells 总被引:15,自引:0,他引:15
Periplasmic permeases are composed of four proteins, one of which has an ATP-binding site that has been postulated to be involved in energy coupling. Previous data suggested that these permeases derive energy from substrate level phosphorylation (Berger, E. A. (1973) Proc. Natl. Acad. Sci. U.S.A. 70, 1514-1518); however, conflicting results later cast doubt upon this hypothesis. Here, we make use of two well characterized periplasmic permeases and of a well characterized unc mutant (ATPase-) to examine this energetics problem in depth. We have utilized the histidine and maltose periplasmic permeases in Escherichia coli as model systems. Isogenic unc strains were used in order to study separately the effect of the proton-motive force and of ATP on transport. These parameters were analyzed concomitantly with transport assays. Starvation experiments indicate that both histidine and maltose transport require ATP generation and that a normal level of delta psi is not sufficient. Uncouplers such as carbonyl cyanide-m-chlorophenylhydrazone and 2,4-dinitrophenol dissipated the delta psi without decreasing the ATP level and without significant effect on these permeases, showing that delta psi is not needed. Inhibition of ATP synthesis by arsenate eliminates transport through both permeases, confirming the need for ATP. In agreement with previous results with the glutamine permease (Plate, C. A. (1979) J. Bacteriol. 137, 221-225), valinomycin plus K+ dissipates delta psi without affecting ATP levels and inhibits histidine transport; however, maltose transport is not inhibited under these conditions. This result is discussed in terms of the artefactual side effects caused by valinomycin/K+ treatment on some periplasmic permeases. Histidine transport is also shown to be sensitive to changes in the cytoplasmic pH. It is concluded that periplasmic permeases indeed have an obligatory requirement for ATP (or a closely related molecule), whereas the proton-motive force is neither sufficient nor essential. 相似文献
138.
Reconstitution of periplasmic transport in inside-out membrane vesicles. Energization by ATP 总被引:16,自引:0,他引:16
The periplasmic histidine permease of Salmonella typhimurium has been reconstituted in inside-out vesicles (IOV) of Escherichia coli by disrupting the cells with a French press in the presence of a high concentration of the periplasmic histidine-binding protein, HisJ. Efflux from IOV, which is equivalent to uptake in whole cells, is induced by ATP. The reconstituted system depends on the presence of the membrane-bound permease proteins, HisQ, HisM, and HisP, and does not function if reconstitution is performed in the presence of a mutant HisJ protein, HisJ5625, that can bind histidine normally but can't interact properly with the membrane complex. Efflux is not induced by the nonhydrolyzable ATP analog, adenyl-5'-yl imidodiphosphate, supporting the contention that ATP hydrolysis is necessary. 8-Azido ATP inactivates IOV, indicating that the ATP effect occurs through the HisP protein, which has previously been shown to be modified by 8-azido ATP (Hobson, A., Weatherwax, R., and Ames, G.F.-L. (1984) Proc. Natl. Acad. Sci. U. S. A. 81, 733-7337). The estimated Km of the vesicles for ATP is about 200 microM. Vanadate, an inhibitor of phosphohydrolase enzymes, inhibits ATP-induced efflux. We conclude that ATP is likely to be the proximal energy source for periplasmic permeases. 相似文献
139.
Bioassay of vitamin A compounds 总被引:1,自引:0,他引:1
S R Ames 《Federation proceedings》1965,24(4):917-923
140.
Yen Ying Lim Victor L. Villemagne Simon M. Laws David Ames Robert H. Pietrzak Kathryn A. Ellis Karra Harrington Pierrick Bourgeat Ashley I. Bush Ralph N. Martins Colin L. Masters Christopher C. Rowe Paul Maruff for the AIBL Research Group 《PloS one》2014,9(1)