Dual DNA and BSA targeting by a novel Pd(II) complex: Correlation of spectroscopic, hydrodynamic, docking, and...

A new metal complex of ethylenediamine and sulfosalicylic acid, incorporating Pd²⁺ as metal ion, was synthesized and analyzed using spectroscopic, electrochemical, physicochemical and quantum mechanical methods. Quantum mechanical calculations identified the lowest-energy structure for the new compound. The metal center adopts a four-coordinate, slightly distorted square planar geometry. Molecular electrostatic potential surface and HOMO - LUMO analysis were accomplished for the obtained structure. The compound demonstrated promising cytotoxic activity against K562 cancer cells, with an IC₅₀ value of 36 μM. The biological activity was assessed by investigating interactions with calf-thymus DNA (CT-DNA) and bovine serum albumin (BSA) using UV-Vis and fluorescence spectroscopy. Hydrogen bonds/van der Waals interaction with K_b (CT-DNA) = 1.71 × 10⁵ and K_b (BSA) = 1.00 × 10⁵ were determined. Viscosity and electrophoresis experiments for CT-DNA and circular dichroism (CD) for BSA were also applied to further investigate the binding of the title complex with the mentioned biomolecules. Viscosity assay confirmed the groove binding with CT-DNA, and CD suggested the refolding of BSA in the presence of Pd(II) complex. Molecular docking modeling predicted the groove binding with CT-DNA and positioning in site I of BSA through some hydrogen bonds.