Binding parameters and molecular dynamics of β-lactoglobulin-vanillic acid complexation as a function of pH- part B: Neutral pH

Interactions between the dimeric form of beta-lactoglobulin and vanillic acid were investigated at pH 7.2, using a variety of spectroscopic techniques and molecular dynamics (MD) simulations. FTIR and CD studies showed alterations in the secondary structure of the protein upon its interaction with the ligand. Fluorescence measurements indicated that the dimeric complex with the phenolic acid produced a large dissociation constant (KD) compared to the monomeric counterpart at acidic pH (part A of this series). Stoichiometry of 1:1 was identified for the beta-lactoglobulin-vanillic acid complex by Job plot analysis at neutral pH suggesting two ligand molecules can participate in binding with the dimer. Molecular docking and MD simulations suggested that the top-ranked binding sites of the ligand were located at the entrance of each beta-barrel structure of the dimer. These simulations also allowed identification of the contribution of water molecules, in the form of protein-water-ligand bridging interactions, to the complexes.

Automated summary

The study investigated the interactions between the dimeric form of beta-lactoglobulin and vanillic acid using various spectroscopic techniques and molecular dynamics (MD) simulations. Results showed changes in the protein's secondary structure upon interaction with the ligand, with a 1:1 stoichiometry for the complex at neutral pH. Molecular docking and MD simulations indicated the top-ranked binding sites of the ligand and the contribution of water molecules to the complexes.