Investigation of the Interaction of Antitumor Palladium and Platinum Complexes of Ethyldithiocarbamate with Human Serum Albumin

In this work, two Platinum (II) and Palladium (II) complexes of 2,2'-bipyridine (bpy) and diethyldithiocarbamate (Et-dtc) with anti-tumor activity against K562 were selected. The Cc50 values of Pd and Pt compounds are 55 and 89 micromolar, respectively that are lower than cisplatin. These complexes interacted with human serum albumin (HSA) in Tris-buffer containing 10 mM NaCl, pH=7.4 at 27 and 37 °C by spectroscopic methods. Results obtained from denaturation studies indicate that probably Pd(II) complex denature the HSA while the Pt(II) does not so. Isothermal titration data indicated that the stability of protein decrease by increasing complex concentration and the denaturation process is exothermic. Binding of these cationic complexes with HSA occurs by electrostatic interaction. These complexes can denature HSA at very low concentrations of the micromolar spatially platinum complex. Fluorescence studies showed the intensity of HSA quenched in the presence of each Pt or Pd complex and quenching mechanism seems to be static. Circular dichroism spectra of HSA were recorded and the percentage of alpha helicity in the presence of Pd and Pt complexes were investigated 5 and 3%, respectively.