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141.
142.
Perturbation of nifT expression in Klebsiella pneumoniae has limited effect on nitrogen fixation. 总被引:1,自引:1,他引:0
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In the nitrogenase system of Klebsiella pneumoniae, nifT is located between nifDK, the structural genes for dinitrogenase, and nifY, whose product is involved in nitrogenase maturation. It is, therefore, a reasonable hypothesis that the NifT protein might also have a role in the maturation of nitrogenase. However, the phenotypic characterization of nifT and nifT-overexpressing strains for effects on the regulation, maturation, and activity of nitrogenase identified no properties that were distinct from those of the wild type. We conclude that the K. pneumoniae NifT protein is not essential for nitrogen fixation under the conditions examined. 相似文献
143.
Elizabeth S. Woo Yukihiro Kondo Simon C. Watkins Dale G. Hoyt John S. Lazo 《Experimental cell research》1996,224(2):365
Metallothionein (MT), a major zinc-binding intracellular protein thiol, has been associated with cytoprotection from heavy metals, antineoplastic drugs, mutagens, and cellular oxidants. Despite its small mass (7 kDa), nuclear partitioning of MT has been observed in both normal and malignant tissues. The factors controlling MT sequestration are unknown. Thus, we examined the regulation of MT subcellular distribution in human cancer cell lines that exhibit prominent nuclear MT. The nuclear disposition of MT was unaltered during cell cycle passage in synchronized cells. MT redistributed to the cytoplasm when cells were exposed to reduced temperature. Cytoplasmic redistribution was also seen in DU-145 and HPC36M prostatic cancer cells after ATP depletion, but not in PC3-MA2 and SCC25/CP cells. Pretreatment with 10 μMCdCl2did not significantly alter MT distribution but did render all cells sensitive to cytoplasmic redistribution after either reduced temperature or ATP depletion. Thus, nuclear retention of MT is energy requiring and this ability of MT to accumulate in subcellular compartments against its concentration gradient may be important in the capacity of MT to supply Zn or other metals to target sites within the cell. 相似文献
144.
Harry Adams Neil A. Bailey Philippe Bertrand Simon R. Collinson David E. Fenton Simon J. Kitchen 《Inorganica chimica acta》1996,250(1-2):139-148
The cyclocondensation of 2,5-diformylthiophene and the amines N,N-bis-(2-aminoethyl)-2-phenylethylamine, N,N-bis-(2aminoethyl)-t-butyl-amine and N,N-bis-(2-aminoethyl)-t-butyl-amine in the presence of silver(I) salts yields homodinuclear bibracchial tetraimine Schiff base macrocyclic complexes. The structures of two such complexes are also reported. The complex Ag2L4(NO3)(PF6) (2) crystallises in the triclinic space group
, No. 2) and has unit-cell dimensions a = 12.834(6), B = 13.183(6), C = 14.588(7) Å, = 64.86(4), β = 79.77(4), γ = 69.44(3)° with Z = 2; there is a monodentate and singly bridging nitrate anion present and the Ag---Ag separation is 4.161 Å. The complex Ag2L4(CH3CN)2(BF4)2·CH3CN (9) crystallises in the triclinic space group
, No. 2) and has unit-cell dimensions a = 9.297(4), B = 12.985(3), C = 21.770(5) Å, = 91.570(10), β = 92.33(3), γ = 97.92(3) ° with Z = 2; there is a strongly bonded acetonitrile molecule coordinated to each silver atom and the Ag---Ag separation is 4.920 Å. 相似文献
145.
The arsenical resistance operon of IncN plasmid R46 总被引:3,自引:0,他引:3
Debby F. Bruhn Jiaxin Li Simon Silver Francisco Roberta Barry P. Rosen 《FEMS microbiology letters》1996,139(2-3):149-153
146.
James K. Friel Claude Mercer Wayne L. Andrews Brian R. Simmons Simon E. Jackson 《Biological trace element research》1996,54(2):135-142
Contamination in a trace element laboratory can come from a variety of sources, including laboratory gloves. Therefore, vinyl
and latex gloves were obtained from as many manufacturers as would supply gloves. These gloves were either prepared for acid-washing
and subsequent soaking in an acid solution, or immersed in an acid solution for a duration of either 1 min or 1 h. Incubation
washes were analyzed for a variety of trace elements by flame atomic abosrption spectroscopy (AAS) or inductively coupled
mass spectrometry (ICP-MS). Results indicated that only three brands of vinyl gloves were acceptable for use in a trace element
laboratory, whereas others had contamination of different elements. Latex gloves contained such high levels of biologically
important elements that they were not considered suitable for routine trace element work. Vinyl gloves of choice should be
routinely acid-washed before use in a trace element laboratory. 相似文献
147.
148.
Uncultivated plants growing on disturbed sites may be useful for assessing the bioavailability of some metals in soils, and thus the potential for metal mobilization up the terrestrial food chain, an important element in ecological risk assessment. A planted chicory cultivar (Cichorium intybus L. var. foliosum Hegi.) and the uncultivated plants horseweed (Canada fleabane) (Erigeron canadensis L.) and dogfennel (Eupatorium capillifolium (Lam.) Small) were evaluated for their ability to act as index plant species for soil Cd, Cr, Ni, and V at two field sites where these metals had been applied five yr previously to two highly weathered sandy Ultisols. Soil Cd was available to all analyzed plant tissues of all three plant species at both sites, particularly on the sandier Blanton soil. Chicory was an effective index plant for Cd on the finer textured Orangeburg soil but functioned as an indicator plant (toxicity symptoms were observed) on the sandier Blanton soil. Horseweed and dogfennel were effective index plants for Cd in both contaminated soils. Soil Cr, Ni, and V were less bioavailable than soil Cd and plant metal uptake was more sensitive to residual soil Cr, Ni, and V than was soil extraction with double acid. Horseweed and chicory may have potential as index plants for soil Cr. Chicory may have potential as a Ni index plant. Chicory and dogfennel may have potential as V index plants. 相似文献
149.
ChimpanzeesPan troglodytes in Kibale National Park, Uganda occasionally swallow entire leaves ofRubia cordifolia (Rubiaceae) without chewing them. The leaves are subsequently egested with minimal damage and no sign of any significant
digestion. Similar behavior reported elsewhere has been proposed to have medicinal effects. Here we test the hypothesis that
chemical components in swallowed leaves have negative effects on intestinal nematodes. We used anin vitro assay to detect the effects of methanol extracts ofR. cordifolia leaves on nematodes,Strongyloides spp., cultured from feces. Control extracts were distilled water, methanol solution, and methanol extracts of food items
that were chewed, rather than swallowed, by chimpanzees. Effects of experimental or control solutions were assayed by nematode
motility. There was no difference in nematode motility among control and experimental extracts. This study therefore did not
support the hypothesis of pharmacological self-medication via leaf swallowing. 相似文献
150.
Thehigh growth(hg) locus in mice produces a 30–50% increase in weight gain of homozygous individuals. Here we report that the microsatellite markerD10Mit69is deleted in high growth mice. The deletion ofD10Mit69was uncovered in a screen of the high growth mouse and its progenitor strains for available markers in thehgregion. We demonstrate thathgandD10Mit69cosegregate in a cross of congenic strains C57BL/6J-hghg× C57BL/6J. These results suggest that deletion of a region aroundD10Mit69is responsible for the high growth effect. MarkerD10Mit69will be utilized as an entry point to physical cloning of thehg-containing segment. A dense map of markers aroundhgconstructed here should allow identification of markers in homologous regions in domestic animals and humans, which may be utilized to assess the role of thehglocus in these other species. 相似文献