Complexation reaction of metal ions with peptide systems. Part XIV. A potentiometric study of rare earth complexes of L-leucylglycylglycine

Abstract Amino acids and dipeptides are of biological importance and therefore their metal complexes are of special interest. Many workers have studied the complexes of various peptides with different transition metals in solution 1 – 5 . Although the stability of complexes of lanthanum with amino acids has been studied 6 – 11 , no work appears to have been done with dipeptide systems. In continuation to our previous work 12, 13 on the complexation reactions of lanthanides with dipeptide systems, the present communication reports the stability constants and thermodynamic functions of Y(III), La(III), Ce(III), Pr(III) and Nd(III) with glycyl-L-proline in aqueous medium at 25, 35 and 45°C at 0.15 M (KNO 3 ) ionic strength. The Calvin—Bjerrum titration technique 14, 15 as modified by Irving and Rossotti 16 was used.