Comparative study of binding interactions between three organometallic rhodium(III) complexes with curcuminoid ligands and human serum albumin

Organometallic rhodium(III) complexes with curcuminoid ligands attracted considerable attention in biological-related fields and the variation of curcuminoid ligands may regulate the biological activity of these organometallic rhodium(III) complexes. To deeply evaluate the biological influences of these complexes, the binding interactions between three rhodium(III) complexes with curcuminoid ligands and human serum albumin (HSA) were comparably investigated by spectroscopic and electrochemical techniques. The results suggested that the intrinsic fluorescence of HSA was quenched by three complexes through static fluorescence quenching mode. Three complexes bonded with Sudlow's siteIof HSA to form ground-state compounds under the binding forces of van der Waals interactions, hydrogen bonds formation, and protonation. Finally, the native conformational structure and the thermal stability of HSA were all changed. Space steric hindrance of complexes took part in the differences of the fluorescence quenching processes, and the chemical polarity of the complexes played a vital role in the variations of the structure and biological activity of HSA. These results illustrated the molecular interactions between protein and organometallic rhodium(III) complexes with curcuminoid ligands, offering new insight about the prospective applications of analogical rhodium(III) complexes in biomedicine areas.