Monitoring the Interactions of a Ternary Complex Using NMR Spectroscopy: The Case of Sugars, Polyphenols, and Proteins

Gaining insight into intermolecular interactions between multiple species is possible at an atomic level by looking at different parameters using different NMR techniques. In the specific case of the astringency sensation, in which at least three molecular species are involved, different NMR techniques combined with dynamic light scattering and molecular modeling contribute to decipher the role of each component in the interaction mode and to assess the thermodynamic parameters governing this complex interaction. The binding process between a saliva peptide, a polyphenol, and polysaccharides was monitored by following 1H chemical shift variations, changes in NMR peak areas, and size of the formed complex. These NMR experiments deliver a complete picture of the association pathway, assessed by dynamic light scattering and molecular dynamics simulations: all of the data collected converge toward a comprehensive mode of interaction in which sugars indirectly play a role in astringency by sequestering part of the polyphenols, reducing their effective concentration to bind saliva proteins.