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采用硼氢化钠还原法制备10nm的纳米银。纳米银在NaCl作用下会发生聚集,在469nm产生一个较强共振散射峰,在pH值为6．8的Na2HPO4-NaH2PO4缓冲液中,半胱氨酸（Cys）吸附在纳米银表面,使纳米银聚集程度减弱,导致体系在469nm的共振散射峰减弱。在选定条件下,Cys浓度在5-300nmol／L范围内与469nm的共振散射光强度减弱值△I469nm呈线性关系,回归方程为△I469=11．55C＋387．92,相关系数和方法检出限分别为0．998、0．5nM。该法可用于草莓汁添加剂半胱氨酸的含量的检测,结果满意。 相似文献
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Ramesh C. Kamboj Neera Raghav Ashwani Mittal Shiwani Khurana Rachna Sadana Hari Singh 《Indian journal of clinical biochemistry : IJCB》2003,18(2):39-47
The cysteine proteinases like cathepsins B, L and H are main hydrolytic enzymes present in lysosomes and play an important
role in intracellular protein degradation. Tuberculosis and leprosy, both are tissue- destructive diseases. Main drugs used
in chemotherapy of these diseases may inhibit the main lysosomal cysteine proteinases i.e. cathepsins B, L and H released
during tissue destruction and thus prevent the further destruction of tissue by these enzymes. So the aim of this study is
to see the effect of antituberculous and antileprotic drugs on these proteolytic enzymes. The effect of commonly used antituberculous
and antileprotic drugs was screened on the activities of purified brain lysosomal cysteine proteinases namely cathepsins B
[EC 3.4.22.1], L [EC 3.4.22.15] and H [EC 3.4.22.16]. Among the antileprotic drugs, only clofazimine inhibited the enzymic
activities whereas dapsone had no effect whatsoever. In antituberculous drugs, rifampicin was the most inhibitory while isoniazid
had little inhibitory potency. Streptomycin and pyrazinamide did not effect the activities at all. As regards the mechanism
of inhibition, clofazimine and isoniazid inhibited the enzymes in a non-competitive manner with K values of 0.25 mM and 5.0
mM for cathepsin B, 0.071 mM and 0.833 mM for cathepsin L and 1.513 mM and 0.885 mM for cathepsin H, While rifampicin could
effect in a competitive manner with Ki values of 0.03 mM, 0.125 mM and 0.027 mM for cathepsin B, L and H respectively. 相似文献
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