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111.
V C Tsang K R Tsang K Hancock M A Kelly B C Wilson S E Maddison 《Journal of immunology (Baltimore, Md. : 1950)》1983,130(3):1359-1365
A systematic and quantitative search was conducted to identify and isolate a serologically pertinent antigen with high specific activity and low cross-reactivity from adult worms of Schistosoma mansoni. Adult worms of S. mansoni quickly thawed from liquid N2 temperatures were disrupted by controlled homogenization in isotonic buffered sucrose. Differential centrifugation of the homogenate yielded three particulate and one soluble fractions: the 480 x G pellet (nuclear), the 7650 x G pellet (mitochondrial), the 360,000 x G pellet (microsomal), and the 360,000 x G supernatant (cytosol). Quantitative analysis indicated a major concentration of specific antigenic activities in the microsomal fraction. Further purifications of the urea-solubilized, n-butanol-treated microsomal particles by gel filtration and ionic-exchange chromatography resulted in a microsomal antigen (MAMA) possessing high specific activity and low cross-reactivity. The final purification post-ionic exchange chromatograph showed a 30-fold increase of specific antigen activity over that of the cytosol fraction. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunotransfer blot by the "Western blot" technique (EITB) indicated specific antigenic activities in association with several different m.w. bands (heterogeneous m.w. by extrapolation = 4.3 to 11.9 x 10(6), 2.0 x 10(5), and 2.0 x 10(4) daltons) of the MAMA fraction. When compared with other reported serologic antigens, MAMA showed substantially higher specific activity and lower cross-reactivity. 相似文献
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Amino acid transport systems I and III in Neurospora are inhibited by amino acids in the intracellular pool (transinhibition). The transinhibition is system specific. The ability of an amino acid to transinhibit a transport system is highly correlated with its affinity for the system. The significance of the system specificity of transinhibition is discussed. 相似文献
114.
Attractant-Directed Motility in Escherichia coli: Requirement for a Fluid Lipid Phase 总被引:8,自引:4,他引:4
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Attractant-directed motility (chemotaxis) in Escherichia coli has an absolute requirement for a fluid membrane. No such requirement was detected for motility per se. 相似文献
115.
Summary Uranyl sulphate (0.2–0.9 mM) inhibited ferrous iron oxidation by growing cultures ofThiobacillus ferrooxidans. The addition of 5–100 mM uranium to the cultures caused immediate cessation of carbon dioxide fixation, rapid loss of viability
and gradual depression of ferrous iron oxidation. Virtually no uranium was found in washed cells grown in the presence of
subtoxic to toxic amounts of uranyl sulphate. Uranium-poisoned organisms appeared plasmolyzed in electron micrographs. Cultures
tolerant to 5 mM UO2
2+ were develoepd by successive subculturing in increased uranium concentrations. The tolerance was maintained during subculturing
in uranium-free medium. Frequency of mutants resistant to 1.0 and 1.5 mM UO2
2+ was 1 per 1.3×106 and 1 per 9.0×108, respectively. The frequency was increased in the presence of 15–150 mM nickel, zinc and manganese. In liquid cultures, bivalent
cations and EDTA alleviated the toxicity of 2 mM uranyl sulphate. 相似文献
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1. Pea-seed phosphofructokinase was purified 27-fold by a combination of fractionation with ethanol and ammonium sulphate. Under the conditions of assay, the enzyme was strongly inhibited by phosphoenolpyruvate. This inhibition was reversed by increasing the concentration of fructose 6-phosphate or magnesium chloride, or by lowering the ATP concentration. 2. Citrate, ADP and AMP inhibited phosphofructokinase and increased the sensitivity to phosphoenolpyruvate inhibition. Sulphate and inorganic phosphate stimulated the enzyme activity and decreased the sensitivity to phosphoenolpyruvate. 3. In the presence of inorganic phosphate and low concentrations of ATP, inhibition by phosphoenolpyruvate ceased and phosphoenolpyruvate became stimulatory. 4. The possible significance of these results in the control of plant carbohydrate metabolism is discussed. 相似文献
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