Spectroscopy, docking and molecular dynamics studies on the interaction between cis and trans palladium-alanine complexes with calf-thymus DNA and antitumor activities

The present article investigates whether the cis and trans isomers of the same compound affect their antitumor and DNA-binding properties. Thus, we have synthesized cis-[Pd(L-Ala)(2)] (I) and trans-[Pd(L-Ala)(2)] (II) (Ala = L-alanine) complexes by modifications to improve the reported procedure. Cytotoxicity tests of these two isomers along with carboplatin (as a known drug) against MCF-7 and HCT-116 (as cancerous) and MCF10A and CCD-841 (as normal cell lines) were performed under the same experimental conditions. The results follow the sequence I > II > carboplatin for both cell lines. DNA-binding studies were carried out in a medium similar to that of physiological conditions (pH = 7 and 0.02 M NaCl). Results of UV-vis absorption provides apparent binding constant, K-app, and midpoint transition of native CT-DNA to refolded structure, L-1/2, suggesting interaction at quite low concentrations of these metal complexes. Fluorescence emission intensity of the CT-DNA-EB system demonstrates static quenching predominates in the binding process. Moreover, negative values of Delta H-0 and Delta S-0 suggested that the hydrogen bonds and van der Waals forces are the interaction forces between the complexes with the CT-DNA groove. Other studies include gel electrophoresis, viscosity experiments, partition coefficient, computational energy minimization, molecular docking and molecular dynamics simulations. All these studies indicate that the cis isomer has better interaction towards CT-DNA and are in accord with fluorescence, UV-vis and cytotoxicity studies. The present work gives valuable indications for further design of cis and trans metal-based isomers as potential anticancer agents.