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101.
The microsomal fraction of Saccharomyces cerevisiae has been shown to catalyse the NADPH-dependent reduction of ergosta-5,7,22,24(28)-tetraen-3β-ol to ergosterol. This cell-free system together with whole-cell cultures of polyene-resistant mutants has been used to compare the rates of reduction of other 24-methylene sterols. The results indicate that the enzyme involved exhibits a marked specificity for ergosta-5,7,22,24(28)-tetraen-3β-ol and support the concept of a major terminal step in ergosterol biosynthesis. 相似文献
102.
Mode of formation of cholesta-5,7-dien-3β-ol from cholest-5-en-3β-ol by larvae of Calliphora erythrocephala 下载免费PDF全文
1. The conversion of cholest-5-en-3beta-ol (cholesterol) into cholesta-5,7-dien-3beta-ol by axenic Calliphora erythrocephala larvae was demonstrated. 2. The transformation is probably direct (Delta(5)-->Delta(5,7)) and does not involve a Delta(0) intermediate (Delta(5)-->Delta(0)-->Delta(7)--> Delta(5,7)). 3. Delta(7)-bond formation involves the stereospecific elimination of the 7beta hydrogen atom. 4. The relative amounts of free and esterified sterols were determined in larvae grown on cholesterol as sole sterol source and on 5alpha-cholestan-3beta-ol supplemented with minimal amounts of cholesterol. 5. The significance of the results is assessed in relation to the probable role of cholesta-5,7-dien-3beta-ol as an intermediate in the biosynthesis of ecdysones. 相似文献
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The largest non-unit eigenvalue λ of the transition matrix for the Wright-Fisher Markov chain model of random genetic drift is found numerically with selective advantages of genotypes taken into account. Polynomials in the selection coefficients are fitted to λ in order to summarize the behaviour of λ with varying selection. Also found are the values of the selective advantages which give rise to an acceleration to the rate of fixation of alleles. These values are compared to results for the diffusion approximation to the Wright-Fisher model. 相似文献
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Trevor Baines 《BMJ (Clinical research ed.)》1985,291(6501):1050-1051
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Trevor Lukey Kuldeep Neote John F. Loman Ardythe E. Unger Fred G. Biddle Floyd F. Snyder 《Biochemical genetics》1985,23(3-4):347-356
An improved method for detecting four Np-1 (purine nucleoside phosphorylase) alleles in mouse erythrocytes by cellulose acetate electrophoresis is described. The previous linkage of Np-1 and Es-10 (esterase-10) was confirmed, with a map distance of 13.0±2.6 cM. Np-2 was detected by either specific activity assay or starch gel electrophoresis and shown to be linked to Es-10, 15.9 ± 3.1 cM, on chromosome 14. No recombinants between Np-1 and Np-2 were observed in 52 offspring, indicating either that these loci are either closely associated or that Np-2 represents simply a property of existing allelic products of the Np-1 locus.This research was supported by Medical Research Council of Canada grants to F.G.B. and F.F.S. 相似文献
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