Binding Studies of a Schiff Base Compound Containing a 1,2,4-Triazole Ring with Bovine Serum Albumin Using Spectroscopic Methods

摘要

The binding interaction of a Schiff base compound containing a 1,2,4-triazole ring[4-(4-chlorobenzyl-ideneamino)-5-methyl-1,2,4-triazole-3-thiol,CTT]with bovine serum albumin(BSA)was studied by spectroscopy methods including fluorescence and circular dichroism spectrum under simulative physiological conditions.Fluo-rescence investigation revealed that the fluorescence quenching of BSA was induced by the formation of a relative stable CTT-BSA complex.The corresponding binding constants(Ka)between CTT and BSA at three different temperatures were calculated according to the modified Stern-Volmer equation.The enthalpy change(ΔH())and entropy change(ΔS())were calculated to be-15.78 kJ·mol-1 and 49.23 J·mol-1·K-1,respectively,which suggested that hydrophobic forces and hydrogen bond played major roles in stabilizing the CTT-BSA complex.Site marker competitive experiments indicated that the binding of CTT to BSA primarily took place in sub-domain IIIA(site Ⅱ)of BSA.The binding distance(r)between CTT and the tryptophan residue of BSA was obtained to be 4.3nm based on F(o)rster theory of non-radioactive energy transfer.The conformational investigation revealed that the presence of CTT decreased the α-helix content of BSA(from 58.62% to 54.66%)and induced the slight unfolding of the polypeptides of protein,which confirmed some micro-environmental and conformational changes of BSA molecules.