Synthesis, characterization, DNA and HSA binding studies of isomeric Pd (II) antitumor complexes using spectrophotometry techniques

Two new Palladium(II) isomeric complexes, [Pd (Gly)(Leu)](I) and [Pd (Gly)(Ile)](II), where Gly is glycine, and Leu and Ile are isomeric amino acids (leucine and isoleucine), have been synthesized and characterized by elemental analysis, molar conductivity measurements, FT-IR, ¹H NMR, and UV–Vis. The complexes have been tested for their In vitro cytotoxicity against cancer cell line K₅₆₂ and their binding properties to calf thymus DNA (CT-DNA) and human serum albumin (HSA) have also been investigated by multispectroscopic techniques. Interactions of these complexes with CT-DNA were monitored using gel electrophoresis. The energy transfer from HSA to these complexes and the binding distance between HSA and the complexes (r) were calculated. The results obtained from these studies indicated that at very low concentrations, both complexes effectively interact with CT-DNA and HSA. Fluorescence studies revealed that the complexes strongly quench DNA bound ethidium bromide as well as the intrinsic fluorescence of HSA through the static quenching procedures. Binding constant (K_b), apparent biomolecular quenching constant (k_q), and number of binding sites (n) for CT-DNA and HSA were calculated using Stern–Volmer equation. The calculated thermodynamic parameters indicated that the hydrogen binding and vander Waals forces might play a major role in the interaction of these complexes with HSA and DNA. Thus, we propose that the complexes exhibit the groove binding with CT-DNA and interact with the main binding pocket of HSA. The complexes follow the binding affinity order of I > II with DNA- and II > I with HSA-binding.