半胱氨酸铜络合物的生成及其结构的研究

本文研究了在不同pH值下,半胱氨酸与CuCl_2络合生成的三种不同的络合物。在酸性溶液中,半胱氨酸与CuCl_2通过络合反应、自氧化还原反应,最后生成带氯桥的络合物Cu_2(Ⅰ)Cl_2(cysH_2)]的白色粉末,(cysH_2为半胱氨酸)。在碱性溶液中,若反应在空气中进行,半胱氨酸与CuCl_2经氧化还原反应,结果生成天蓝色络合物(Cu_2(Ⅱ)(cyss)_2],(cyss~(2-)为胱氨酸根);若反应在绝氧条件下进行,它们则先络合,然后二聚成黑色络合物Cu_2(Ⅱ)(cys)_2·6H_2O)。根据化学分析以及IR和ESR谱的研究,推测了这三种络合物的可能结构。

STUDIES ON THE FORMATION AND THE STRUCTURE OF CYSTEINE-COPPER COMPLEXES

Three complexes have been formed in acidic and basic solutions by the reaction of CuCl2 with cysteine. It is found that in acidic solution the reaction of cysteine and CuCl2 gave a unstable purple complex, in which the cysteine is oxidized to oystine and Cu(Ⅱ) ion is reduced to Cu(Ⅰ) ion. Then the Cu(Ⅰ) ion is combined with the rssidual cysteine to form complex (Ⅰ) Cu2(Ⅰ)Cl2(cysH2)2]. When the cysteine is added into an ajkaline Cu(Ⅱ) solution and the reaotants ere stirred under the atmosphere for 5-6 hours a very stable pale blue complex (Ⅱ) Cu2(Ⅱ)(cyss)2) can be obtained. In basic solution cysteine. is oxidized to cystine, and Cu(Ⅱ) ion is reduced to Cu(Ⅰ) ion. The Cu(Ⅰ) ion in alkaline solution, however, is extremely unstable, and thus is readily oxidized by oxygen in the atmosphere to Cu(Ⅱ) ion. Therefor. in alkaline solution the copper acts actually as a carrier of eleotren transmission or a catalyst. At last a stable complex (Ⅱ) of Cu(Ⅰ) io(?) with cystine is formed. If the above reaction is carried out in the absence of oxygen in basic solution, then a diamagnetic black complex (Ⅲ) Cu2(Ⅱ)(cys)2 6H2O] can be obtained. The possible structures of these three complexes have been deduced from the information of ESR, IR and chemical analysis.