SPECTROSCOPIC AND POTENTIOMETRIC STUDIES ON THE INTERACTION OF TRANS-[(MEH(2),N)(2)PT(MCYT)(2)PDCL]NO3 (MCYT=1-METHYLCYTOSINATE) WITH DERIVATIVES OF AMINO-ACIDS

The interaction of the mixed-metal complex trans-[(MeH(2)N)(2)Pt(mcyt) (2)PdCl]NO3 (mcyt = 1-methyl-cytosinate) with various derivatives of a mino acids mimicking the side-chain metal binding sites of proteins we re studied by H-1 NMR, spectrophotometric and potentiometric methods. The derivatives included N-acetylamino acids (N-acetyl-methionine, -cy steine -lysine, -histidine and -histamine), amino acids (glycine and m ethionine) and dipeptides (Gly-Met and Gly-Lys). The coordination of i ndependent thioether, amino or imidazole nitrogen side-chain donor gro ups resulted in the formation of stable mono- or di-nuclear adducts. T he formation of dinuclear complexes was characteristic of dipeptides a nd N-acetyl-histidine and -histamine. The existence of linkage isomers was demonstrated in the latter case, the Pd-N(3) (imidazole) isomers being more favoured. The possibility of stable chelate formation with palladium(ii) (e.g. S,O for N-acetylcysteine and S,N for methionine) s ignificantly enhanced the decomposition of the mixed-metal complex, le ading to trans[Pt(NH(2)Me)(2)(Hmcyt)(2)](2+).