Ternary complexes involving copper(II) and amino acids,peptides and DNA constituents. The kinetics of hydrolysis of α-amino acid esters

Binary and ternary complexes of copper(II) involving picolylamine (Pic) and amino acids, peptides (HL) or DNA constituents have been investigated. Ternary complexes of amino acids or peptides are formed by simultaneous reactions. Amino acids form the Cu(Pic)L complex, whereas peptides form Cu(Pic)L and Cu(Pic)(LH_–1). The ternary complexes of copper(II) with picolylamine and DNA are formed in a stepwise process, whereby binding of copper(II) to picolylamine is followed by ligation of the DNA components. The stability of the ternary complexes is compared with the stabilities of the corresponding binary complexes. The hydrolysis of glycine methyl ester (MeGly) is catalysed by the Cu(pic)²⁺ complex. The kinetic data is fitted assuming that the hydrolysis proceeds in two steps. The first step, involving coordination of the amino acid ester by the amino and carbonyl groups, is followed by rate-determining attack by the OH^– ion. The second step involves equilibrium formation of the hydroxo-complex, Cu(pic)(MeGly)(OH), followed by intramolecular attack.