Investigation of the binding properties of 3,4-dihydroxybenzaldehyde from Salvia miltiorrhiza (Bunge) with human serum albumin via multi-spectroscopic and molecular docking techniques

Abstract

To investigate the binding properties of 3,4-dihydroxybenzaldehyde with human serum albumin, as well as the structural changes of human serum albumin under a simulated physiological pH value (a pH of 7.4) and a high 3,4-dihydroxybenzaldehyde concentration, a series of techniques, i.e., fluorescence, synchronous fluorescence, ultraviolet-visible absorption, Fourier-transform infrared spectroscopy, and molecular docking simulation, were employed. Steady state fluorescence showed that 3,4-dihydroxybenzaldehyde quenched the intrinsic fluorescence of human serum albumin via a static mechanism. The 3,4-dihydroxybenzaldehyde-human serum albumin complex had a strong affinity (Kb = 105 M-1) at various temperatures. It was shown that 3,4-dihydroxybenzaldehyde was bound to the IB subdomain of human serum albumin primarily via hydrogen bonding and van der Waals forces at high 3,4-dihydroxybenzaldehyde concentrations, based on the results of the thermodynamic and molecular docking. Furthermore, the fluorescence emission spectrum and Fourier-transform infrared spectroscopy results indicated that the binding distance between 3,4-dihydroxybenzaldehyde and human serum albumin was 4.42 nm. In addition, 3,4-dihydroxybenzaldehyde induced conformational changes of human serum albumin. These findings provide reasonable evidence for further understanding the distribution of 3,4-dihydroxybenzaldehyde when it spreads into human blood serum, which may be helpful in food and medicine research.