Effect of ethanol or/and captopril on the secondary structure of human serum albumin before and after protein binding

Abstract

The attenuated total reflection/Fourier transform infrared technique has been utilized to characterize secondary structural changes in human serum albumin (HSA) before and after protein binding via incubation of HSA in different concentrations of ethanol, captopril or ethanol/captopril mixture. The results indicate that ethanol induced a transition from β-sheet to an α-helical structure and promoted conversion of intramolecular hydrogen-bonded β-sheet to intermolecular hydrogen-bonded β-sheet. In contrast, captopril or captopril/ethanol mixture induced conversion of intramolecular hydrogen-bonded β-sheet to intermolecular hydrogen-bonded β-sheet and resulted in exposure of the aromatic side-chain groups in the unfolding conformation of HSA. Thus, protein binding between HSA and captopril or captopril/ethanol seems to play an important role in protein secondary structure.