Influence of non-coordinated aliphatic side chains of amino acids on the hydrophobic interactions involving purine nucleotide complexes

Abstract

Interaction of bivalent Co, Ni, Cu and Zn metal ions with purine nucleotides (5′-guanosine monophosphate and 5′-inosine monophosphate) and aliphatic amino acids (alanine,α-aminobutyric acid, norvaline and norleucine) has been investigated in solution by potentiometricpH measurements at 35°C and 0·10 M (KNO3) ionic strength. The stability constants of binary (1:1) and ternary (1:1:1) complexes of various systems were determined. The stabilization of the ternary complexes is measured in terms of Δlog K, which is the difference between the stabilities of binary and ternary complexes. The influence of aliphatic amino acid side chains on hydrophobic interactions in these systems were identified and rationalised. Species distribution curves were generated using a computer program in order to identify the stable species at biologicalpH.