Complex-formation between polypeptides and metals. 1. Application of various experimental methods to the glycine–copper system

Abstract

The following methods were studied with a view to their application to the reactions between metals and polypeptides in aqueous solution: (a) potentiometric titration, (b) copper-electrode potential measurements, (c) electrophoresis, and (d) spectro-photometric observations. When these methods were applied to the study of complex formation between glycine and cupric ions they confirmed the view that 2 complexes ML+ and ML2 are formed. Even in alkaline solution and with an excess of glycine there was no evidence from the electrophoretic observations of the formation of a complex with a negative charge such as would be found if one cupric ion combined with more than 2 glycine anions. Absorption curves in the visible range of the spectrum were calculated for the copper-glycine complexes.