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排序方式: 共有266条查询结果,搜索用时 15 毫秒
251.
Genetic analysis and cellular localization of the Rhizobium host specificity-determining NodE protein. 总被引:19,自引:0,他引:19 下载免费PDF全文
H P Spaink J Weinman M A Djordjevic C A Wijffelman R J Okker B J Lugtenberg 《The EMBO journal》1989,8(10):2811-2818
The nucleotide sequence of the nodE gene of Rhizobium trifolii strain ANU843 was determined. Like the nodE gene of R. leguminosarum strain 248 it encodes a protein with a predicted mol. wt of 42.0 kd. The predicted NodE proteins of R.trifolii and R.leguminosarum have a homology of 78%. Using antibodies raised against the NodE protein of R.trifolii it was shown that the NodE products of R.leguminosarum and R.trifolii are localized in the cytoplasmic membrane. Furthermore, these NodE proteins are predicted to contain at least two non-polar transbilayer alpha-helices. The nodE genes of R.trifolii and R.leguminosarum were separated from the nodF genes that precede them in the respective nodFE operons. Using the resulting clones, in which NodE was produced under control of the flavonoid-inducible nodABCIJ promoter of R.leguminosarum, it was shown that the NodE product is the main factor that distinguishes the host range of nodulation of R.trifolii and R.leguminosarum. Hybrid nodE genes, which consist of a 5' part of the R.leguminosarum nodE gene and a 3' part of the R.trifolii gene, were constructed. From the properties of these hybrid genes it was concluded that a central region of 185 amino acids at the most, containing only 44 non-identical amino acids, determines the difference in the host-specific characteristics of the two NodE proteins. 相似文献
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Previous studies of the effect of carbonation on taste perception have
suggested that it may be negligible, manifesting primarily in increases in
the perceived intensity of weak salt and sour stimuli. Assuming CO2
solutions in the mouth stimulate only trigeminal nerve endings, this result
is not altogether surprising; however, there are neurophysiological data
indicating that CO2 stimulates gustatory as well as trigeminal fibers. In
that case, carbonation might alter the quality profile of a stimulus
without producing substantial changes in overall taste intensity--much as
occurs when qualitatively different taste stimuli are mixed. To address
this possibility, subjects were asked to rate the total taste intensity of
moderate concentrations of stimuli representing each of the basic tastes
and their binary combinations, with an without added carbonation. They then
subdivided total taste intensity into the proportions of sweetness,
saltiness, sourness, bitterness and 'other taste qualities' they perceived.
The addition of carbonation produced only small increases in ratings of
total taste intensity. However, rather dramatic alterations in the quality
profiles of stimuli were observed, particularly for sweet and salty tastes.
The nature of the interaction is consistent with a direct effect of
carbonation/CO2 on the gustatory system, although the possibility that at
least some of the observed effects reflect trigeminal-gustatory
interactions cannot be ruled out.
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KARI BJØRNERAAS BRAM VAN MOORTER CHRISTER MOE ROLANDSEN IVAR HERFINDAL 《The Journal of wildlife management》2010,74(6):1361-1366
Abstract: Animal locations estimated by Global Positioning System (GPS) inherently contain errors. Screening procedures used to remove large positional errors often trade data accuracy for data loss. We developed a simple screening method that identifies locations arising from unrealistic movement patterns. When applied to a large data set of moose (Alces alces) locations, our method identified virtually all known errors with minimal loss of data. Thus, our method for screening GPS data improves the quality of data sets and increases the value of such data for research and management. 相似文献
258.
PhoE protein pore of the outer membrane of Escherichia coli K12 is a particularly efficient channel for organic and inorganic phosphate 总被引:7,自引:0,他引:7
This study was undertaken to investigate the proposed in vivo pore function of PhoE protein, an Escherichia coli K12 outer membrane protein induced by growth under phosphate limitation and to compare it with those of the constitutive pore proteins OmpF and OmpC. Appropriate mutant strains were constructed containing only one of the proteins PhoE, OmpF or OmpC, or none of these proteins at all. By measuring rates of nutrient uptake at low solute concentrations, the proposed pore function of PhoE protein was confirmed as the presence of the protein facilitates the diffusion of Pi through the outer membrane, such as a pore protein deficient strain behaves as a Km mutant. Comparison of the rates of permeation of Pi, glycerol 3-phosphate and glucose 6-phosphate through pores formed by PhoE, OmpF and OmpC proteins shows that PhoE protein is the most effective pore in facilitating the diffusion of Pi and phosphorus-containing compounds. The three types of pores were about equally effective in facilitating the permeation of glucose and arsenate. Possible reasons for the preference for Pi and Pi-containing solutes are discussed. 相似文献
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van Alphen Wim Lugtenberg Ben Berendsen Wim 《Molecular genetics and genomics : MGG》1976,147(3):263-269
Molecular Genetics and Genomics - Mutants ofEscherichia coli K12, deficient in up to three major outer membrane proteinsb,c andd have been constructed. Mutants that lack the lipopolysaccharide... 相似文献