Über die Verbindungen von Zink mit Glykokoll, Cystein, Cystin und Glutathion und über die Natur der Bindung zwischen Insulin und Zink

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Abstract
When solns. of Zn salts and amino acids were brought together, Zn complex compounds were formed. The nature of these compounds was investigated by potentiometric titra-tion with the glass electrode. In more dilute solns., 1 mol of Zn combined with 1 mol of glycine, while in more conc. solns., especially in the presence of excess glycine, 1 mol of Zn combined with 2 mols of glycine. Complex compounds were formed between Zn and glycine, cystine, cysteine and glutathione, in which the carboxyl and amino groups took part. Similar compounds were formed between Zn and insulin. Insulin was precipitated from soln. at pH 6.5 in the presence of increasing amts. of Zn. Analysis of the dried precipitate showed that the insulin was saturated at from 2.7-35% Zn. Between 29 and 37 carboxyl groups were combined with Zn. The authors were not able to crystallize the compounds of high Zn content. Ordinary-crystalline insulin contains 0.38-050% Zn.

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