INFLUENCE OF NONCOORDINATED ALIPHATIC SIDE-CHAINS OF AMINO-ACIDS ON THE HYDROPHOBIC INTERACTIONS INVOLVING PURINE NUCLEOTIDE COMPLEXES

Interaction of bivalent Co, Ni, Cu and Zn metal ions with purine nucle otides (5'-guanosine monophosphate and 5'-inosine monophosphate) and a liphatic amino acids (alanine, a-aminobutyric acid, norvaline and norl eucine) has been investigated in solution by potentiometric pH measure ments at 35 degrees C and 0.10 M (KNO3) ionic strength. The stability constants of binary (1:1) and ternary (1:1:1) complexes of various sys tems were determined. The stabilization of the ternary complexes is me asured in terms of Delta log K, which is the difference between the st abilities of binary and ternary complexes. The influence of aliphatic amino acid side chains on hydrophobic interactions in these systems we re identified and rationalised. Species distribution curves were gener ated using a computer program in order to identify the stable species at biological pH.