Effects of chlorogenic acid on the binding process of cadmium with bovine serum albumin: A multi-spectroscopic and docking study

Abstract

Chlorogenic acid (CGA), a natural phenolic product, plays an increasingly positive role in removing the toxicity of heavy metals owing to its antioxidative activity and metal-chelating properties. Cadmium (Cd), as a ubiquity heavy metal, can enter the human body and increase health risk. In this study, we investigated the effects of CGA on conformational changes of Cd2+-induced bovine serum albumin (BSA) by multiple spectroscopic methods, including ultraviolet–visible (UV–vis), fluorescence and circular dichroism spectroscopy (CD), as well as molecular docking. The result of the fluorescence spectroscopy revealed that the binding constant of (Cd2+-CGA)-BSA was smaller than that of Cd2+-BSA at 298 K (6.34 × 102 L/mol vs 22.7 × 102 L/mol). UV–vis spectroscopy described that the CGA could reduce the changes on the main chain structure of BSA induced by the high concentrations Cd2+ (8 and 16 × 10−4 mol/L). CD results showed an increase in α-helix content from 60% in Cd2+-BSA to 70% in (Cd2+-CGA)-BSA interaction, whereas β-sheet content decreased from 7% to 4%, the random coil content decreased from 33% to 26%, which indicating that the chelation of CGA with Cd2+ reduced the unfolding in the protein peptide chain and enhanced the hydrophobicity of BSA induced by Cd2+ alone. The data of Forsters resonance energy transfer proved that CGA reduced the structural changes of BSA by shortening the distance between Cd2+ and BSA. The computational techniques indicated that CGA might reduce the interaction of Cd2+ with BSA by forming hydrogen bonds with Cd2+. The findings in our study will provide a useful reference for exploring the effect of CGA on Cd2+-induced changes in albumin function.