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361.
On the basis of published data, a detailed model of the active centre of Escherichia coli peptidyl transferase is proposed. The major conclusions are as follows: A binding site is present at each of the acceptor (A′) and donor (P′) substrate binding sites of the enzyme for the 3′-terminal CpCpA of aminoacyl- and peptidyl-tRNA, respectively. In particular, the acceptor CpCpA binding site is composed of sites for the following groups: the terminal adenine, the first phosphoryl residue from the 3′-terminus, the 3′-penultimate cytosine, and the second 3′-CMP residue. In addition, two binding sites are present on each of the A′ and P′ sites, one for the basic and one for the hydrophobic aminoacyl R groups of both aminoacyl-tRNA and the carboxyl-terminal amino acid of peptidyl-tRNA. The role of these sites in the binding of inhibitors and substrates and in the mechanism of catalysis of peptide bond formation by peptidyl transferase is discussed. 相似文献
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Poor resolution, retarded progress of DNA through gels, and variable sizing of DNA fragments between and within gels hinder
accurate genotyping of some simple sequence length polymorphism (SSLP) markers with the Perkin Elmer Applied Biosystems 377
Sequenator. These problems are similar to renaturation related problems observed in DNA sequencing gels. PCR products especially
susceptible to these problems are shown to have higher melting temperatures (Tm) than others. Gels containing increased concentrations of denaturants allow greater accuracy in allelic discrimination. This
is especially beneficial where quantification is necessary.
Received: 7 February 2000 / Accepted: 16 March 2000 相似文献
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J D Symons 《Prostaglandins, leukotrienes, and essential fatty acids》1990,39(2):159-165
Two studies were performed to examine the relationship between Prostacyclin (PGI2) and high density lipoprotein cholesterol (HDL-C). A longitudinal study examined the stable metabolite of PGI2, 6-keto PGF1 alpha, along with HDL-C, and total cholesterol (TC) before (Week 0), during (Week 4), and after (Week 9) an eight week aerobic conditioning program. 6-keto PGF1 alpha was measured by radioimmunoassay using 125I, and HDL-C and TC were spectrophotometrically analysed. Maximal oxygen uptake and resting heart rate data obtained at Week 0 confirmed that the training group (E) was not different from the sedentary group (C). Results obtained at Week 9 indicated that maximal oxygen uptake was higher (p less than 0.05) and resting heart rate lower (p less than 0.05) in the E group, while these variables remained unchanged in group C. Levels of 6-keto PGF1 alpha, HDL-C, and TC did not differ between groups E and C when Week 0 was compared with Week 9. However, within the E group, significantly lower concentrations of 6-keto PGF1 alpha (p less than 0.05) and HDL-C (p less than 0.05) were found at Week 4 compared with Week 0. A cross-sectional study involving 52 subjects examined the relationship between 6-keto PGF1 alpha and several cardiovascular disease risk factors which included HDL-C. The only significant correlation (r = 0.50 p less than 0.05) observed was between 6-keto PGF1 alpha and HDL-C. 相似文献