DNA/BSA interactions of new gold(III) complexes with some pyridine- containing ligands

Abstract

Pyridine-containing ligands, 4,5-diazafluoren-9-one (dafone) and pyrazino[2,3- f][1,10]phenanthroline (ppz), were used for the synthesis of two novel gold(III) complexes, [AuCl3(dafone)] (Au1) and [AuCl2(ppz)][AuCl4] (Au2). In this study, we investigated their interactions with bovine serum albumin (BSA) and calf thymus DNA (ct-DNA) using fluorescence emission spectroscopy to assess their binding affinity towards these biomolecules. Considering that serum albumin consists of three domains (I–III), each subdivided into two subdomains (A and B), fluorescence competition experiments were also performed using site-specific markers to locate the binding sites of the complexes. Eosin Y was used as a marker for Site I (subdomain IIA), ibuprofen for Site II (subdomain IIIA), and digitoxin for Site III (subdomain IB). The results, including the calculated binding constants (KA), revealed that both Au1 and Au2 interact with BSA and ct-DNA, with Au1 exhibiting a higher affinity toward ct-DNA. Furthermore, the KA values of both Au1 and Au2 decreased in the presence of eosin Y, indicating that their primary binding site is likely located within Site I of BSA.