兔肝金属硫蛋白稀水溶液的脉冲辐解

金属硫蛋白(Metallothioneins,简称MTs)是一类富含巯基和金属的低分子量蛋白质,广泛存在于哺乳动物中.MTs 通常含61个氨基酸,其中20个为半胱氨酸,不含芳香族氯基酸和组氨酸,因此在280nm 附近没有吸收峰.MTs 通常结合7个Cd 或zn,20个巯基全部去质子化并参与配位,从而形成牢固的结构域.有证据表明MTs 可能有储存Zn 和Cu 的作用,同时能减轻重金属对动物细胞的毒性,但其生理功能一直不很清楚.近几年的研究表明,MTs 能增强机体对电离辐射的耐受力、修复DNA 损伤,这可能与MTs 中含有丰富的巯基有关.体外实验测得k_(MT/OH)=10~(12)dm~3·mol~(-1)·s~(-1),k_(MT/O(?))=5×10~5dm~3·mol~(-1)·s~(-1),但其辐解机理尚不清楚.本工作利用脉冲辐解技术研究了免肝MT-I 稀水溶液辐解时的中间过程,并作了初步的解释.

PULSE RADIOLYSIS OF RABBIT LIVER METALLOTHIONEIN IN AQUEOUS SOLUTION

Metallothioneins(MTs) are widely occuring proteins characterizied by a low molecular weight (6500—6800) and an extremely high metal and sulfur content. The mechanizm of pulse radiolysis of rabbit liver MT-I in aqueous solution was studied. After pulse radiolysis, two peaks occured with maximum absorption at 450 nm and 280 nm. It was supposed that the first peak was due to RSSR~- radical formed by the combination of RS·radical and RS~- anion. The observed kinetic constants of growth and decay of RSSR~- radical were estimated from the absorption spectra.