Comparative investigation of interactions between two ruthenium(II) arene PTA type complexes with curcuminoid ligands and human serum albumin

Ruthenium(II) arene PTA (1,3,5-triaza-7-phosphaadamantane) type complexes with curcuminoid ligands have attracted great attentions in biomedical areas. Investigation of structural influences helps in understanding the biological effects of these complexes. To research their structural influences, the interactions between two ruthenium(II) arene PTA type complexes with curcuminoid ligands and human serum albumin (HSA) were systematically investigated by multispectroscopic techniques and electrochemical methods. The fluorescence spectral results indicated that two complexes bonded with Sudlow's site I of HSA to form 1: 1 complex−HSA compounds. Van der Waals interactions and hydrogen bonds formation were the major binding forces during their complex formation interactions. Subsequently, the intrinsic fluorescence of HSA was statically quenched by these complexes through concentration-dependent manner. The conformation and secondary structure of HSA were all changed at the present of two complexes. The space steric hindrance of complexes was responsible for differences in the fluorescence quenching, while the chemical polarity played important role in the variation of binding interactions between HSA and two complexes. These results provide the molecular understanding of binding interactions between protein and ruthenium(II) arene PTA type complexes with curcuminoid ligands, which gain new insight into the biological applications of similar ruthenium(II) arene derivatives in the future.