Probing the Binding of 4β-(Benzoyl-thioureido)-4-deoxypodophyllotoxin to Human Serum Albumin by Molecular Spectroscopy

Abstract

The binding interaction of 4β-(benzoyl-thioureido)-4-deoxypodophyllotoxin (HY-1) with human serum albumin (HSA) was investigated by fluorescence, UV–visible absorption, and circular dichroism (CD) spectroscopies. The results indicated that binding of HY-1 to HSA caused strong fluorescence quenching of HSA through a static quenching mechanism, hydrogen bond and van der Waals contacts are the major forces in the stability of the HY-1–HSA complex, and the process of the binding of HY-1 with HSA was driven by the enthalpy (ΔH = −41.60 kJ·mol−1). The energy transfer from HSA to HY-1 occurs with high probability. The effect of HY-1 on the conformation of HSA was further analyzed by synchronous fluorescence and CD spectra techniques. The results show that presence of HY-1 decreases the α-helix content of HSA and induces the slight unfolding of the polypeptides of this protein. Additionally, the presence of metal ions (e.g. Zn2+, Cu2+, Fe3+, Co2+, and Ni2+) was found to decrease the binding constant between HY-1 and HSA.