Studies on the interaction between human serum albumin and [Rh2(OAc)2(bpy)2(H2O)2](OAc)2

Absorption, CD, fluorescence, and ICP(AES) methods were used to evaluate the interaction of [Rh2(OAc)2(bpy)2(H2O)2](OAc)2 with human serum albumin (HSA). The rhodium complex reacts easily with HSA; the Rh atoms are coordinated to protein via the imidazole rings of His residues. When the protein was incubated for 24 h at 37 degrees C, the amount of rhodium was found to be approximately 7 mol per mol of HSA. Analysis of CD spectra showed the decreasing helix content to be about 15% in the metal-bound HSA. The relative fluorescence intensity of HSA bound with rhodium decreased to 20% of that of the native state, suggesting that perturbation around the Trp-214 residue took place. This was confirmed by the destruction of the warfarin binding site. The rhodium binding weakens the interaction of HSA with other molecules like heme or bilirubin.