Heme Releasing from Human Hemoglobin upon Interaction with a New Synthesized Complex of 1,10-Phenanthroline-n-butyl Dithiocarbamato Pd(II) Nitrate

Abstract

In the present study, we investigated the effect of a new anticancer Pd(II) complex, 1,10-phenanthroline-n-butyl dithiocarbamato Pd(II) nitrate, on the heme releasing from human hemoglobin (Hb) as well as alterations in the structure and function of Hb using different spectroscopic methods of UV-Vis, fluorescence and circular dichroism (CD)at two temperatures of 25 and 37 °C. Fluorescence data revealed that the Pd (II) complex is able to quench the intrinsic fluorescence of Hb. The binding constant, number of binding sites and thermodynamic parameters at two temperatures were calculated. The values of <em>ΔH°, ΔS°,</em> and <em>ΔG°</em> indicated that the van der Waals force or hydrogen bond interactions might play a major role in the interaction of complex with Hb. The far-UV-CD studies displayed that the regular secondary structure of Hb had no significant changes. To evaluate the functional changes of Hb <em>via</em> destruction of the heme structure, fluorescence studies were performed at excitation wavelengths of 321 nm and 460 nm with emission wavelengths of 465 nm and 525 nm, respectively. The results demonstrated that two fluorescent heme degradation products are found during the interaction of Pd(II) complex with Hb. The results of thermal behavior of Hb studied at 415 nm confirmed the heme degradation, which referred to decrease in the hemoglobin stability in the presence of Pd(II) complex. Also, the cytotoxic effects and anti-tumor activity of the complex against human breast cell line, T47D were carried out using MTT assay. The Cc₅₀value obtained after different incubation times of 24 and 48 h. The finding related to structural and functional changes of Hb induced by Pd(II) complex may be important to improve understanding of side effects of new designed metal anti-cancer drugs undergoing.