Understanding molecular interaction between thermally modified beta-lactoglobulin and curcumin by multi-spectroscopic techniques and molecular dynamics simulation

This study elucidated the binding of curcumin (CUR) onto preliminary thermally modified beta-lactoglobulin (beta-LG). beta-LG at pH 8.1 was heated at 75 degrees C, 80 degrees C and 85 degrees C for 10 min to construct denatured proteins (beta-LG75, ss-LG80, beta-LG85). Steady and time-resolved fluorescence studies uncovered that CUR quenched proteins in simultaneous static and dynamic mode. Pre-heating beta-LG improved its binding with CUR and the strongest affinity occurred in beta-LG80. Fluorescence resonance energy transfer (FRET) analysis indicated that binding distance between CUR and beta-LG80 was the smallest and energy transfer was the most efficient. beta-LG80 had the highest surface hydrophobicity. Fourier-transform infrared (FT-IR) spectroscopy and differential scanning calorimeter (DSC) confirmed that CUR transferred from crystal to amorphous state after association with protein and revealed the contribution of hydrogen bonds. Combination of beta-LG80 with CUR retained the antioxidant capacity of each component. Molecular dynamics simulation demonstrated enhanced hydrophobic solvent accessible surface area of beta-LG80 compared with native protein. Data obtained from this study may provide useful information for comprehensively understanding the ability of beta-lactoglobulin to bind hydrophobic substances under different environmental conditions like high temperature and alkaline medium.

Automated summary

This study investigated the binding of curcumin (CUR) with thermally modified beta-lactoglobulin (beta-LG). Different temperature conditions were used to modify beta-LG, and the results showed that pre-heating at 80 degrees C led to the strongest binding affinity. The interaction between CUR and beta-LG80 involved hydrogen bonds and resulted in the transfer of CUR to an amorphous state, while maintaining the antioxidant capacity of both components. Molecular dynamics simulation confirmed the enhanced hydrophobic properties of beta-LG80 compared to native protein.