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51.
The sulfhydryl groups of the thiol-dependent cytolytic toxin from Bacillus alvei evidence for one essential sulfhydryl group 总被引:4,自引:0,他引:4
C Geoffroy A M Gilles J E Alouf 《Biochemical and biophysical research communications》1981,99(3):781-788
Alveolysin, an extracellular protein toxin (Mr ? 63,000) excreted by Bacillus alvei and purified to homogeneity was shown to contain four cysteine residues. All thiol groups of the hemolytically active toxin preparation were free as found by direct titration by 5,5′-dithiobis (2-nitrobenzoic acid) and confirmed by the absence of disulfide bond. Toxin alkylation with tosyl lysine chloromethyl ketone resulted in the complete loss of hemolytic activity and the disappearance of only one thiol group with no modification of histidine residues. These results support the conclusion that one essential thiol group is implicated in the membrane-disrupting activity of alveolysin. 相似文献
52.
Hans-Dietrich Heilmann Maria Holzner 《Biochemical and biophysical research communications》1981,99(4):1146-1152
To achieve specific cross-linking between the active sites of the non-identical subunits tryptophan synthase from E. coli was modified by a novel method. After reaction with bifunctional reagents of the isolated subunits at their active sites, the tetrameric complex was formed and the free ends of the reagent molecules reacted with each other forming a covalent bridge between the subunits. The distance between the amino acid side chains involved in the cross-linking should not exceed approx. 1.8 nm. A distance much shorter than that is unlikely since all attempts to cross-link the active sites with different shorter bifunctional reagents failed. The implications of these results in the mechanism of action of the enzyme are discussed. 相似文献
53.
H. Stam H. Jansen W.C. Hülsmann 《Biochemical and biophysical research communications》1980,96(2):899-906
Chylomicron degradation by hearts from fed and fasted rats was studied using a perfusion technique, which allows the separate collection of coronary (Qrv) and interstitial effluent (Qi). Upon perfusion with [3H]-cholesterol-containing chylomicrons the tissue recovery of label was highest in the fasted state, while label recovered in Qi was highest in the fed state. Density gradient centrifugation of Qi indicated that the label was recovered in lipoproteins with higher densities: low density lipoproteins (1.019<d<1.050), high density lipoproteins (1.050<d<1.21) and a fraction of d>1.21. These particles probably represent chylomicron degradation products (remnants and “surface fragments”). Our results indicate that tissue cholesterol uptake during chylomicron degradation may be inhibited in the fed state. Furthermore, the role of the myocyte (or interstitial) lipoprotein lipase in chylomicron degradation is discussed. 相似文献
54.
The cytotoxic and mutagenic properties of antitumor drugs such as adriamycin, acridines, diacridine, actinomycin D and Pt compounds are related to their interaction with nucleic acids and inhibition of protein synthesis. We have examined their interaction with human erythrocyte ghost membranes and murine mastocytoma cells using spin labeling techniques. These drugs induce changes in electron spin resonance of the spin labeled ghost membranes and in the mastocytoma cells. These alterations suggest that these drugs induce changes in protein conformation of the membranes. The membrane binding properties of these drugs may be important in their mechanism of action. 相似文献
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56.
Cain G. D. and Bassow F. 1976. Porphyrins in the perienteric fluid of Ascaris lumbricoides. International Journal for Parasitology6: 79–82. Porphyrins in the perienteric fluid of adult female A. lumbricoides were esterified in methanolic H2SO4, extracted in chloroform, separated by thin-layer chromatography, and identified spectrophotometrically before and after conversion to their zinc and copper chelates. Protoporphyrin IX was the major component, comprising 95·4% of the total; the remaining 4·6 % was coproporphyrin III. Uroporphyrin was not detected; no porphyrins were recovered from other worm tissues. Fluid from worms with light and dark colored guts varied in protoporphyrin content from 0·58 to 4·08 nmoles/ml, respectively, but fluid from both groups contained similar molar ratios of protoporphyrin, coproporphyrin and heme. 相似文献
57.
Three new bases were isolated from Banisteriopsis caapi; they are harmine N-oxide, harmic acid methyl ester (methyl 7-methoxy-β-carboline 1-carboxylate) and harmalinic acid (7-methoxy-3,4-dihydro-β-carboline 1-carboxylic acid). 相似文献
58.
The product of hydrolysis of the active principle of the herbicide Bidisine® is degraded in at least two different ways. One way gives p-chlorobenzoic acid. The other, more important one, gives a conjugate with l-cysteine, which is further oxidized. The ability to oxidize the conjugate provided a means of distinguishing between susceptible and resistant plant species. 相似文献
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