Thermodynamics of the reactions of [Pd(Et4en)(H2O)2]2+ with ligands of biological significance: deactivation of based-drug by the sulfur-containing biomolecules

Abstract

The reaction of [Pd(Et4en)(H2O)2]2+ (Et4en=N,N,N′,N′-tetraethylethylenediamine) with amino acids, peptides, dicarboxylic acids or DNA constituents was investigated at 37°C and 0.16 M ionic strength. The stoichiometry and stability of the complexes formed were determined and the binding centers of the ligands were assigned. The concentration distribution diagrams of the complexes were evaluated. The equilibrium constants for the displacement of representative coordinated ligands such as inosine, glycine or methionine by mercaptoethylamine were calculated and the concentration distribution diagrams of the various species were evaluated. Pd(Et4En)Cl2 complex, where Et4En = N,N,N′,N′-tetraethylethylenediamine, was synthesized and characterized by elemental analysis and spectroscopic technique. The complex formation equilibria was investigated. The displacement of coordinated inosine (A) by cysteine (B) was studied. The equilibrium constant for the displacement reaction given is given by