pH modulates grass carp myofibrillar protein-aldehyde interactions: Molecular mechanistic insights

The interactions between grass carp myofibrillar proteins (MPs) and selected aldehydes under different pH conditions were analyzed. The results showed that the binding capacity of MPs to the aldehydes followed the order: nonanal > octanal > hexanal, and their binding capacity increased with rising pH (5-9). MPs-aldehyde interactions exhibited static and dynamic quenching, predominantly mediated by hydrophobic forces, with pH exerting no effect on the quenching mode. With the increase of pH, the imolecular quenching constant, binding constant, and binding sites number of MP and aldehyde gradually increased. Meanwhile, MPs-aldehyde interactions modulated the microenvironment of tryptophan and tyrosine residues, with elevated pH levels amplifying this effect. The presence of aldehydes significantly and differentially reduced the secondary structure in MPs at different pH conditions. Besides, molecular docking result revealed that pH affected the interaction between grass carp proteins and aldehydes by thier altering the binding sites and binding free energy.