钴（Ⅱ）与金属硫蛋白的反应

REACTION OF CO(Ⅱ) WITH METALLOTHIONEIN

研究了Ｃｏ（Ⅱ）和金属硫蛋白反应的动力学，发现反应分三段进行，由此得到了不同条件下各段对应的假一级反应速率常数．假设金属硫蛋白中每个金属结合２０／７个ＳＨ基团，用盐酸滴定Ｃｏ５Ｔｈ（ｔｈｉｏｎｃｉｎ）和Ｃｏ７Ｔｈ，根据它们的紫外光谱特征波长处吸收值降至５０％时的ｐＨ，分别１４０到它们的表观平均稳定常数．并且第一次发现当金属硫蛋白中钴逐步增加时．紫外吸收不断增强，但结合５个Ｃｏ时即已达到应大，而不是７个Ｃｏ．最后根据这些结果，对Ｃｏ（Ⅱ）与金属硫蛋白反应的机理进行了讨论．

he propertics of reaction of Co(Ⅱ) with rabbit liver MT have been investigated. The reaction is characterized by triphasic kinetics and the corresponding pseudo-first order rate constants arc determined under different conditions. Assuming each metal binding to 20/7 SH groups, average stability constants of Co7Th and Co5Th are obtained from hydrogen ions concentration required for 50% loss of the spectra absorbance. Interestingly,it was found that the absorption intensitics of Co-thiolate adduct, formed by adding Co to apoMT for varied ratio of co(Ⅱ) to MT, reach a maxium after 5 mol cquivalent co(Ⅱ) rather than 7 cobalt. All the above data give an deep insight into the mechanism of the reaction between cobalt and MT.