Conformational and Ion Binding Properties of a Cyclic Octapeptide, $cyclo(Ala-Leu-Pro-Gly)_2$

Abstract

The conformation and ion-binding characteristics of a cyclic octapeptide, $cyclo(Ala-Leu-Pro-Gly)_2$, in a liphophilic solvent, acetonitrile, have been studied using CD and nmr spectroscopy. The peptide binds preferentially to divalent cations such as calcium, magnesium, and barium. The conformations of the free cyclic peptide and its calcium complex are very similar with well-defined \beta and \gamma-turns. The cyclic peptide readily forms equimolar and possibly 2 : 1 (peptide:cation) complexes with divalent cations