NMR and molecular modeling of wine tannins binding to saliva proteins: revisiting astringency from molecular and colloidal prospects

• Published in: The FASEB journal 2010-11, Vol.24 (11), p.4281-4290
• Main Authors: Cala, Olivier, Pinaud, Noël, Simon, Cécile, Fouquet, Eric, Laguerre, Michel, Dufourc, Erick J, Pianet, Isabelle
• Format: Article
• Language: English
• Subjects: Antioxidants - chemistry; Antioxidants - metabolism; Astringents; Biflavonoids - chemistry; Biflavonoids - metabolism; Catechin - chemistry; Catechin - metabolism; Colloids - chemistry; Dimerization; DOSY NMR; Humans; hydrophilic interactions; hydrophobic interactions; Magnetic Resonance Spectroscopy; Models, Molecular; molecular dynamics; Molecular Dynamics Simulation; Molecular Structure; Proanthocyanidins - chemistry; Proanthocyanidins - metabolism; procyanidins; proline‐rich‐proteins; Protein Binding; Salivary Proteins and Peptides - chemistry; Salivary Proteins and Peptides - metabolism; STD NMR; Tannins - chemistry; Tannins - metabolism; Vitaceae; Wine
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.10-158741

In organoleptic science, the association of tannins to saliva proteins leads to the poorly understood phenomenon of astringency. To decipher this interaction at molecular and colloidal levels, the binding of 4 procyanidin dimers (B1-4) and 1 trimer (C2) to a human saliva proline-rich peptide, IB7₁₄, was studied. Interactions have been characterized by measuring dissociation constants, sizes of complexes, number, and nature of binding sites using NMR (chemical shift variations, diffusion-ordered spectroscopy, and saturation transfer diffusion). The binding sites were identified using molecular mechanics, and the hydrophilic/hydrophobic nature of the interactions was resolved by calculating the molecular lipophilicity potential within the complexes. The following comprehensive scheme can be proposed: 1) below the tannin critical micelle concentration (CMC), interaction is specific, and the procyanidin anchorage always occurs on the same three IB7₁₄ sites. The tannin 3-dimensional structure plays a key role in the binding force and in the tannin's ability to act as a bidentate ligand: tannins adopting an extended conformation exhibit higher affinity toward protein and initiate the formation of a network. 2) Above the CMC, after the first specific hydrophilic interaction has taken place, a random hydrophobic stacking occurs between tannins and proteins. The whole process is discussed in the general frame of wine tannins eliciting astringency.--Cala, O., Pinaud, N., Simon, C., Fouquet, E., Laguerre, M., Dufourc, E. J., Pianet, I. NMR and molecular modeling of wine tannins binding to saliva proteins: revisiting astringency from molecular and colloidal prospects.