Nickel(II)-Schiff base complex recognizing domain II of bovine and human serum albumin: spectroscopic and docking studies.

It has been spectroscopically monitored that a mononuclear nickel(II)-Schiff base complex {[NiL]·CH(3)OH=NSC} exhibits greater binding affinity for bovine serum albumin (BSA) than that of its human counterpart (HSA). Moreover the modes of binding of NSC with the two serum albumins also differ significantly. Docking studies predict a relatively rare type of 'superficial binding' of NSC at domain IIB of HSA with certain mobility whereas for BSA such phenomena has not been detected. The mobile nature of NSC at domain IIB of HSA has been well correlated with the spectroscopic results. It is to be noted that thermodynamic parameters for the NSC interaction also differ for the two serum albumins. Occurrence of energy transfer between the donor (Trp of BSA and HSA) and acceptor (NSC) has been obtained by means of Förster resonance energy transfer (FRET). The protein stability on NSC binding has also been experimented by the GuHCl-induced protein unfolding studies. Interestingly it has been found that NSC-HSA interaction enhances the protein stability whereas NSC-BSA binding has no such impact. Such observations are indicative of the fact that the conformation of NSC is responsible in recognizing the two serum albumins and selectively enhancing protein stability.