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61.
Summary A brief review is presented of the Vester-Ulbricht -decay Bremsstrahlen hypothesis for the origin of optical activity, and of subsequent experiments designed to test it. Certain of our experiments along these lines, begun in 1974 and involving the irradiation of racemic and optically active amino acids in a 61.7 KCi90Sr–90Y Bremsstrahlen source, have now been completed and are described. After 10.89 years of irradiation with a total Bremsstrahlen dose of 2.5×109 rads, crystallinedl-leucine, norleucine, and norvaline suffered 47.2, 33.6, and 27.4% radiolysis, respectively, but showed no evidence whatsoever of asymmetric degradation.d- andl-Leucine underwent about 48% radiolysis and showed 2.4–2.9% radioracemization. Other samples in solution were too severely degraded to analyze. Probable intrinsic reasons for the failure of the Vester-Ulbricht mechanism to afford asymmetric radiolysis in the present and related experiments involving -decay Bremsstrahlen are enumerated.A portion of this material was presented at the 7th International Conference on the Origins of Life, Mainz, FRG, July 10–15, 1983 相似文献
62.
近年来,常用未经丙酮固定的、由丁酸和巴豆油激活的B95-8细胞或P3HR-1细胞为靶细胞,检测人血清中EB病毒IgA/MA抗体以早期诊断鼻咽癌,效果良好。但由于B95-8细胞含有多种EB病毒抗原,不能用丙酮固定,需多次离心沉淀,在浮悬状态下检测,技术比较复杂。 相似文献
63.
64.
Cd binding capacity and pulse polarography were used to study the inducibility of sulfhydryl groups in cultured Chinese hamster ovary cells (wild type and a Cd-resistant mutant) in response to dexamethasone (dex) and Zn. Evidence is presented that both the wild type and the mutant responded to dex and Zn treatment by induction of sulfhydryl groups. In wild type for Zn and dex as well as in the mutant for dex, this induction seems to be in the form of sulfhydryls attached to particulate or membrane fractions in the cells. For Zn in the Cd-resistant mutant the induction was in the form of metallothionein. 相似文献
65.
Ethionine, a hepatocarcinogen, was administered into rats 24 h before partial hepatectomy and immediately thereafter. Hepatic precursor ribosomal RNA (pre-rRNA) obtained 20 h after the operation of rats injected with ethionine and adenine resulted in methyl deficiency as judged by the incorporation of [3H]methyl group of S-adenosylmethionine into nuclear rRNA by partially purified rRNA methylase. The ethionine and adenine treatment causes methyl deficiency of nuclear rRNA at 2'-hydroxyribose sites of cytidine and uridine, but not at base sites. Although the ethionine and adenine treatment produced no significant change in total hepatic RNA synthesis in vivo assayed by the incorporation of labeled orotate, a one-third increase in nuclear rRNA synthesis as well as a one-third decrease in microsomal rRNA synthesis was found under the treatment. These results suggest that the undermethylation at 2'-hydroxyribose of pre-rRNA in liver nucleus, which is caused by ethionine and adenine administration into rats, causes an inhibition of the processing of nuclear pre-rRNA to cytoplasmic rRNA. 相似文献
66.
S.Y.K. Wen D. Hess J.W. Kauffman J.M. Collins L.J. Lis 《Chemistry and physics of lipids》1983,32(2):165-173
Raman spectroscopy and X-ray diffraction are used to study the effect of heat and Ca2+ on dimyristoylphosphatidylethanolamine dispersions. Unlike phosphatidylcholine dispersions, dimyristoylphosphatidylethanolamine bilayers (at pH 8) require heating above Tm in order for hydration to occur and apparently bind Ca2+ at very low levels. These results are related to models for membrane fusion. 相似文献
67.
Survival of Shigella in Sewage: II. Effect of Glycerol on Shigella flexneri and Shigella Bacteriophage1
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Glycerol (30%) inhibited or delayed the adsorption of Shigella bacteriophage on its host organism, S. flexneri II; glycerol also inhibited or delayed the burst of phage, whether or not adsorption was carried out in the presence of glycerol. Studies of the mechanisms of these effects showed that viscosity and osmotic shock probably were not responsible for either phenomenon. The inhibition of adsorption, however, was proportional to the concentration of glycerol, and appeared to be a function of the hydroxyl groups on the glycerol molecule. The inhibition of burst seemed to be related to the osmotic pressure outside the bacterial cells. 相似文献
68.
69.
用免疫荧光单克隆抗体对脊髓灰质炎病毒抗原表位的分析 总被引:1,自引:0,他引:1
用间接免疫荧光与中和试验筛选出来的抗脊髓灰质炎2型与3型不同毒株的12个单克隆抗体,其中3个仅有免疫荧光活性,9个具有中和与免疫荧光活性。用免疫荧光活性的单克隆抗体进行试验,发现它们在识别特异性抗原表位方面与中和性单克隆抗体相似,显示出株特异的、几个毒株共同特异的或型特异的抗原表位。根据表位分布关系及特征,可以用来鉴别型内毒株的特征、毒株的抗原分析、抗原变异的研究以及疫苗相关病例的鉴别。所得结果与中和性单克抗隆抗体及T1-寡核苷酸指纹图谱分析一致。而免疫荧光单克隆抗体识别抗原表位的活性范围比中和性单克隆抗体更广。另外还发现某些兼有荧光与中和两活性的同一个单克隆抗体,用不同方法(IF与NT)进行试验时,与相同毒株出现不同表位反应,这点是值得引起注意需待进一步证实的重要问题。 相似文献
70.
Reduced glutathione (GSH) inhibited catalase activity in a dose-dependent manner. DL-dithiothreitol (DL-DTT) and dithioerythritol (DTE) also inhibited catalase activity. The inhibition of catalase by GSH and DL-DTT could be reduced by NADPH. Polyacrilamide gel electrophoresis demonstrated the inhibition was partially reversible. The inhibition of catalase by GSH appeared to be partly due to superoxide radicals, since it was inhibited by active manganese superoxide dismutase, but not by heat-inactivated enzyme. Other chemical species also appear to take part in the inhibition, but they could not be identified. 相似文献