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241.
乳链菌肽的分离纯化和部分生物学性质 总被引:1,自引:0,他引:1
用乳酸链球菌SM526进行乳链菌肽的发酵生产,产量为40~50mg/l.经中空纤维超滤器超滤,非极性大孔吸附树脂XAD-2层析,CM-SephadexC-25层析和SephadexG-50层析纯化了该肽。SDS-PAGE表明达均一,RP-HPLC表明其纯度不低于95%。SDS-PAGE测其Mr约为3600,用IEF测其等电点为9.5.酸性条件下稳定且抗热;对胰蛋白酶、胃蛋白酶和木瓜蛋白酶不敏感,但对α-胰凝乳酶和蛋白酶K敏感。乳链菌肽对多种革兰氏阳性菌有强烈的抑制作用;以枯草杆菌和金黄色葡萄球菌为指示菌,其作用方式是杀菌。 相似文献
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Summary Genetic studies have demonstrated biparental inheritance of plastids in alfalfa. The ratio of paternal to maternal plastids in the progeny varies according to the genotypes of the parents, which can be classified as strong or weak transmitters of plastids. Previous cytological investigations of generative cells and male gametes have provided no consistent explanation for plastid inheritance patterns among genotypes. However, plastids in the mature egg cells of a strong female genotype (6–4) were found to be more numerous and larger than in mature eggs of a weak female genotype (CUF-B), and the plastids in 6–4 eggs are positioned equally around the nucleus. In CUF-B, the majority of plastids are positioned below (toward the micropyle) the mid level of the nucleus, which is the future division plane of the zygote. Since only the apical portion of the zygote produces the embryo proper, plastids in the basal portion were predicted to become included in the suspensor cells and not be inherited. In the present study, we examined zygotes and a two-celled proembryo from a cross between CUF-B and a strong male genotype (301), a cross that results in over 90% of the progeny possessing paternal plastids only. Our results indicate that the distribution of plastids observed in the CUF-B egg cell is maintained through the first division of the zygote. Further, paternal plastids are similarly distributed; however, within the apical portion of the zygote and in the apical cell of the two-celled proembryo, the number of paternal plastids is typically much greater than the number of maternal plastids. These findings suggest that maternal and paternal plastid distribution within the zygote is a significant factor determining the inheritance of maternal and paternal plastids in alfalfa. 相似文献
244.
We examined the effect of methionine deficiency on iodothyronine 5’-deiodinase activity in selenium-deficient rats or selenium-sufficient
rats fed sodium selenate or selenomethionine. Forty-two weanling male Wistar rats were divided into six groups and pair fed
the respective purifiedl-amino acid-based diets for 4 wk.l-methionine concentrations in the diet were 8.0 g/kg for sufficient rats, and 2.0 g/kg for deficient rats. Selenium concentrations
in the diet were 0.5 mg/kg (as sodium selenate or selenomethionine) for selenium-sufficient rats and less than 0.005 mg/kg
for selenium-deficient rats. Type I 5’-deiodinase activities were significantly lower in liver and higher in kidney of methionine-deficient
rats than in those of methionine-sufficient rats fed either the selenium-sufficient or the selenium-deficient diets. The type
I 5’-deiodinase activity in brain was significantly lower in the methionine-deficient rats than in the methionine-sufficient
rats fed the selenium-deficient diet. Type II 5’-deiodinase activity in brain was significantly higher in the methionine-deficient
rats than in the methionine-sufficient rats fed selenium-sufficient diet as sodium selenate. Both thyroxine and 3,3’,5-triiodothyronine
concentrations in plasma were significantly higher in the methionine-deficient rats than in the methionine-sufficient rats.
It is suggested that the methionine deficiency affects the 5’-deiodinase activity and thyroid hormones level in the rats. 相似文献
245.
Sequence diversity of V1 and V2 domains of gp120 from human immunodeficiency virus type 1: lack of correlation with viral phenotype. 总被引:5,自引:5,他引:0 下载免费PDF全文
We analyzed by PCR and direct sequencing 57 viral sequences from 47 individuals infected with human immunodeficiency virus type 1, focussing on the V1 and V2 regions of gp120. There was extensive length polymorphism in the V1 region, which rendered sequence alignment difficult. The V2 hypervariable locus also displayed considerable length variations, whereas flanking regions were relatively conserved. Two-thirds of the amino acid residues in these flanking regions were highly conserved (> 80%), presumably reflecting their critical contribution to V2 structure or function. We also characterized the syncytium-inducing properties of the isolates from which we derived sequence information. There was no correlation between V1 or V2 sequences and the viral phenotype, contrary to a previous report (M. Groenink, R. A. M. Fouchier, S. Broersen, C. H. Baker, M. Koot, A. B. van't Wout, H. G. Huisman, F. Miedema, M. Tersmette, and H. Schuitemaker, Science 260:1513-1516, 1993). The sequence heterogeneity described in this study provides information to suggest that it would be most difficult to exploit the V1 and V2 domains for vaccine development. 相似文献
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Mahmood Vahedian Liang Shi Tong Zhu Ronald Okimoto Kathleen Danna Paul Keim 《Plant molecular biology》1995,29(4):857-862
Repetitive DNA sequences comprise a large percentage of plant genomes, and their characterization provides information about both species and genome evolution. We have isolated a recombinant clone containing a highly repeated DNA element (SB92) that is homologous to ca. 0.9% of the soybean genome or about 105 copies. This repeated sequence is tandemly arranged and is found in four or five major genomic locations. FISH analysis of metaphase chromosomes suggests that two of these locations are centromeric. We have determined the sequence of two cloned repeats and performed genomic sequencing to obtain a consensus sequence. The consensus repeat size was 92 bp and exhibited an average of 10% nucleotide substitution relative to the two cloned repeats. This high level of sequence diversity suggests an ancient origin but is inconsistent with the limited phylogenetic distribution of SB92, which is found an high copy number only in the annual soybeans. It therefore seems likely that this sequence is undergoing very rapid evolution. 相似文献
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中国大陆若干群体的黑果蝇的线粒体DNA多态性研究 总被引:13,自引:2,他引:11
本文研究了果蝇D.virilis种群D.virilis线粒体DNA(mitochondrialDNA,mtDNA)的多态性。用9种限制性内切酶XbaⅠ,EcoRⅠ,PstⅠ,HindⅢ,BglⅡ,SacⅠ,ScaⅠ,EcoRV和PuvⅡ,对青岛、南京、上海、宁波与泉州5个D.virilis群体的mtDNA进行了限制性片段长度多态性(restrictionfragmentslengthpolymorphism,RFLP)的研究。在5群体中,发现5种不同的酶切图谱,它们彼此之间的遗传差异π为0.46%-1.76%,群体内遗传差异πij为0.00%-0.33%,群体间的差异dxy,为0.00%-0.82%。分布于中国大陆的D.virilis的群体间遗传差异在总遗传差异中所占比例γst值为24.62%。我们发现,D.virilis的栖息环境对mtDNA的遗传变异有十分明显的影响,而不同地理纬度的群体之间其遗传距离并无倾群(cline)表现。 相似文献