A potentiometric and spectroscopic study of the interaction of angiotensin II and some of its peptide fragments with copper(II)

Abstract

The synthesis is reported of the peptide fragments of angiotensin II, Asp-Arg-Val-Tyr and MeCO-Tyr-IIe-His, together with the results of a potentiometric and spectroscopic (visible, circular dichroism, and e.s.r.) study of the interaction with Cu^II of angiotensin II itself and the peptides. Results show that, in the pH range 6–8, Cu^II appears to co-ordinate to the imidazole nitrogen of the histidyl side-chain together with neighbouring deprotonated peptide nitrogens. When the pH is raised above 8 the co-ordination centre moves to give a complex resembling that found in simple peptides, i.e. through the terminal amino nitrogen and its neighbouring peptide nitrogens.