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91.
梁峥 《Acta Botanica Sinica》1989,31(7):523-528
菠菜叶片过氧体可转变甘油酸或羟基丙酮酸成为丝氨酸。以甘氨酸为氨基供体时,完整过氧体的转变活性比破碎的约高2.5倍,这不是由于完整的膜包被使有效的羟基丙酮酸浓度增加,或由于膜破碎使辅助因子损失,也不是由于过氧体膜的甘氨酸主动运输系统的作用。结果显示,在过氧体中存在甘氨酸转氨酶,完整过氧体中高的转氨速度可能是由于甘氨酸转氨酶在完整的和破碎的过氧体中的构象或构型不同。 相似文献
92.
93.
We have identified two estradiol-dependent single-stranded DNA binding proteins in the nucleus and cytoplasm of chicken hepatocytes that bind the sequence 5'TCACCTTCGCTATG3' in the first exon of the chicken vitellogenin gene. As judged by chromatography on heparin-Sepharose and by proteolytic clipping bandshift assay, the two proteins are different. Furthermore, they only bind to the oligonucleotide corresponding to the upper strand. Depurination and depyrimidination interference experiments with the cytoplasmic protein show that the bases CCTT-G are involved in the protein-DNA interaction. An RNA corresponding to the upper strand of the gene between nucleotide positions -73 and +53 competes for binding to the single-stranded DNA. UV cross-linking experiments performed with bromouridine-substituted single-stranded RNA reveal that an estradiol-dependent hepatocyte cytoplasmic protein with a Mr of 71,000 binds to the mRNA-like single-stranded RNA. 相似文献
94.
Cholera toxin as a mucosal adjuvant. Glutaraldehyde treatment dissociates adjuvanticity from toxicity 总被引:3,自引:0,他引:3
Cholera toxin (CT), either mixed with or conjugated to unrelated protein Ag, is known to enhance the intestinal IgA response of rodents toward the unrelated Ag. Although relatively low doses of CT exert this gut mucosal adjuvant effect, the inherent toxicity of CT is a hindrance to its use in humans. Our report demonstrates that CT treated with 20 mM glutaraldehyde retains adjuvant properties but exhibits more than 1000-fold lower toxicity than untreated toxin. Glutaraldehyde was also used in a one-stage conjugation procedure to couple CT covalently to Sendai virus. Again, toxicity was reduced more than 1000-fold. This drop in toxicity is consistent with an observed 100-fold loss in binding capacity of the CT B subunit and a 20- to 50-fold reduction in adenylate cyclase activation by the CT A subunit. Oral administration of this virus-toxoid conjugate resulted in increased gut antiviral IgA titers compared with oral administration of either virus alone or of virus mixed with glutaraldehyde-treated toxin. This marked decrease in toxicity may afford a practical approach for the use of CT as a mucosal adjuvant. 相似文献
95.
96.
P C Babbitt G L Kenyon B M Martin H Charest M Slyvestre J D Scholten K H Chang P H Liang D Dunaway-Mariano 《Biochemistry》1992,31(24):5594-5604
We have deduced the nucleotide sequence of the genes encoding the three components of 4-chlorobenzoate (4-CBA) dehalogenase from Pseudomonas sp. CBS-3 and examined the origin of these proteins by homology analysis. Open reading frame 1 (ORF1) encodes a 30-kDa 4-CBA-coenzyme A dehalogenase related to enoyl-coenzyme A hydratases functioning in fatty acid beta-oxidation. ORF2 encodes a 57-kDa protein which activates 4-CBA by acyl adenylation/thioesterification. This 4-CBA:coenzyme A ligase shares significant sequence similarity with a large group of proteins, many of which catalyze similar chemistry in beta-oxidation pathways or in siderophore and antibiotic synthetic pathways. These proteins have in common a short stretch of sequence, (T,S)(S,G)G(T,S)(T,E)G(L,X)PK(G,-), which is particularly highly conserved and which may represent an important new class of "signature" sequence. We were unable to find any proteins homologous in sequence to the 16-kDa 4-hydroxybenzoate-coenzyme A thioesterase encoded by ORF3. Analysis of the chemistry and function of the proteins found to be structurally related to the 4-CBA:coenzyme A ligase and the 4-CBA-coenzyme A dehalogenase supports the proposal that they evolved from a beta-oxidation pathway. 相似文献
97.
Comparisons of the site specific binding of nitrobenzylthioinosine (NBMPR) to intact and lysed red cells from various mammalian and avian species suggest the presence of a cytoplasmic pool of nucleoside transporters. In some species the cytoplasmic pool is about 50% of the total (mouse). On the average, the cytoplasmic pool is approx. 20% of the surface pool of NBMPR-binding sites. In sheep reticulocytes, both pools disappear in an energy-dependent manner during the maturation of the reticulocyte in vitro. 相似文献
98.
Yuan Han-min V. D. Keppenne P. S. Baenziger T. Berke G. H. Liang 《Plant Cell, Tissue and Organ Culture》1990,21(3):253-258
Four winter wheat (Triticum aestivum L.) and two spring wheat cultivars were evaluated in anther culture on three to four different media for their ability to initiate callus and green plants. Five media were used in the experiment: stored-potato medium with Ficoll 400, fresh-potato medium with Ficoll 400, fresh-potato medium with agar, fresh-potato liquid medium without agar or Ficoll 400, and a one tep 85D12-3 medium. Greatly different frequencies of calli and/or green plants were obtained from different cultivars and media. The callus initiation frequency varied from 2.7% for Arapahoe to 52% for Pavon, both on the stored potato medium with Ficoll 400. The frequency of green plant regeneration ranged from 0% for Arapahoe and Siouxland on the stored-potato medium with Ficoll 400 and 0% for Redland and Arapahoe in the fresh-potato medium with Ficoll 400 to 12% for Chris in the 85D12-3 medium (one-step procedure). Chris and Centurk 78, previously reported as having high levels of response, had significantly higher (P < 0.05) frequencies of green plant regeneration on the 851312-3 medium than the other cultivars. An unexpected observation is that wet MSC– medium enhanced callus regeneration more than a drier MSC– medium. 相似文献
99.
100.
阿胶冲剂与阿胶的化学成分对比分析研究 总被引:2,自引:0,他引:2
阿胶在我国有着悠久的历史,是常用滋补中药,具有许多特殊的功效,国内外享有盛誉。据《本草纲目》及《本草纲目拾遗》等介绍,阿胶在明代以前系用(沙牛)牛,水牛,驴皮或猪、马、驼皮等杂皮熬制而成。自清代始一律采用黑驴皮熬制。以往服用阿胶必须将阿胶先用水浸泡后,然后加热溶解后才能服用.为了克服这一缺点,山东化工学院研制了一种用开水冲服的阿胶新制剂——阿胶冲剂.为了弄清阿胶经物理方法处理后的化学组成成份与原阿谱的化学组成成分的不同变化。我们对其所含微量元素、氨基酸进行了对比分析.另外,本文首次报道了阿胶及阿胶冲剂的红外光谱分析结果. 相似文献