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Copolymers of γ-methyl D - and L -glutamates with various D /L ratios were prepared. Infrared absorption spectra of solid films were measured and sums of right- and left-handed helix contents were determined from intensities of amide V bands. Farultraviolet absorption spectra and optical rotatory dispersion of these copolymers in solutions are used to ascertain their helical character. Chain conformations of DL -copolypeptides are discussed. 相似文献
75.
Oxidized and reduced nicotinamide adenine dinucleotide phosphate levels of plants hardened and unhardened against chilling injury 总被引:5,自引:4,他引:1
Pea plants (Pisum sativum L. var. Alaska) subjected to low temperature (5°) in the light acquired resistance against chilling injury.
Unhardened plants maintained high NADP and low NADPH levels during illumination at 25° but hardened plants had low NADP and high NADPH levels in the light. When the unhardened plants were transferred to the dark room at 25°, their NADPH levels decreased immediately. On the other hand, hardened plants maintained a high NADPH level for a few hours even in the dark.
相似文献76.
77.
FINE STRUCTURE OF SPINY SPORES OF STREPTOMYCES 总被引:1,自引:0,他引:1
78.
Studies on sea-snake venoms. Crystallization of erabutoxins a and b from Laticauda semifasciata venom 总被引:22,自引:13,他引:9
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1. The toxic principles in the venom of the sea-snake Laticauda semifasciata were separated into two components by CM-cellulose chromatography and obtained in crystalline forms. They were named ;erabutoxins a and b'. 2. The homogeneity of each toxin was shown by rechromatography, by disk electrophoresis, by ultracentrifuging, by toxicity measurements before and after repeated crystallizations and by N-terminal analysis. 3. They had molecular weights of about 7000. Both of them contained 61 (or 62) amino acid residues/molecule. The only difference between erabutoxins a and b was that one of the aspartic acid (or asparagine) residues in erabutoxin a was replaced by a histidine residue in erabutoxin b. 4. Both of the toxins had LD(50) values of 0.15mug./g. body wt. for mice and 0.07mug./g. for rats. It was shown with frog-muscle preparations that they acted on postsynaptic membrane to block neuromuscular transmission. 相似文献
79.
Temperature dependence of proton nuclear magnetic resonance spectra has been followed for cobrotoxin, a postsynaptic neurotoxin fromNaja naja atra venom. Several aromatic amino-acid residues, including the functionally essential Trp-29 located at the tip of the central loop of the molecule, have been found to undergo a thermal structural transition above the global thermal denaturation temperature. It is suggested that a local structure around these residues behaves somehow independently of the rest of the molecule, and that such structural organization may be favorable for a conformational change of a neurotoxin molecule on binding to acetylcholine receptor. 相似文献
80.
Quantitative analysis of serum IL-6 and its correlation with increased levels of serum IL-2R in HIV-induced diseases 总被引:11,自引:0,他引:11
M Honda K Kitamura Y Mizutani M Oishi M Arai T Okura K Igarahi K Yasukawa T Hirano T Kishimoto 《Journal of immunology (Baltimore, Md. : 1950)》1990,145(12):4059-4064
We have devised a luminescence sandwich ELISA for the quantification of IL-6 in both sera and cell culture supernatants, which had a detection limit of 100 fg/ml of test sample. By using the luminescence sandwich-ELISA, low but measurable levels of IL-6 (9.5 pg/ml on average) were found in the sera from normal individuals. The serum levels of IL-6 were elevated in HIV-seropositive asymptomatic carriers (55.5 pg/ml on average), and the IL-6 levels were correlated with the degree of HIV-induced disease progression (AIDS-related complex 106.8 pg/ml on average and (AIDS 283 pg/ml). IL-6 immunoreactivity in the sera of AIDS patients eluted at a 25,000 m.w. major peak, which was biologically active and heat-stable, and a 500,000 m.w. minor peak in size-exclusion HPLC. Interestingly, a significant correlation was observed between the serum IL-6 levels and soluble IL-2R levels. In vitro, HIV infection of PHA-activated PBMC led to enhanced release of IL-6 into the culture supernatants. Moreover, soluble IL-2R release was markedly increased by adding exogenous IL-6, whereas it was decreased by adding the neutralizing anti-IL-6 mAb to the cultures. These results demonstrate that increased IL-6 levels are significantly associated with sIL-2R levels, and suggest a cause of the increased levels of this receptor in patients with HIV infection. Furthermore, both serum IL-6 and serum IL-2R levels in HIV infection reflect the stage of the HIV-induced disease. 相似文献