title: NMR and molecular modeling of wine tannins binding to saliva proteins: revisiting astringency from molecular and colloidal prospects.
abstract: 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, IB7(14), 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 IB7(14) 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.
authors.affiliation: Chemistry and Biology of Membranes and Nanoobjects, Université Bordeaux, Pessac, France.
authors.forename: Olivier
authors.initials: O
authors.lastname: Cala
authors.forename: Noël
authors.initials: N
authors.lastname: Pinaud
authors.forename: Cécile
authors.initials: C
authors.lastname: Simon
authors.forename: Eric
authors.initials: E
authors.lastname: Fouquet
authors.forename: Michel
authors.initials: M
authors.lastname: Laguerre
authors.forename: Erick J
authors.initials: EJ
authors.lastname: Dufourc
authors.forename: Isabelle
authors.initials: I
authors.lastname: Pianet
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000378:metabolism; D001252:Astringents; D044946:Biflavonoids / Q000737:chemistry / Q000378:metabolism; D002392:Catechin / Q000737:chemistry / Q000378:metabolism; D003102:Colloids / Q000737:chemistry; D019281:Dimerization; D006801:Humans; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D044945:Proanthocyanidins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000378:metabolism*; D013634:Tannins / Q000737:chemistry* / Q000378:metabolism*; D014920:Wine
chemical_list: D000975:Antioxidants; D001252:Astringents; D044946:Biflavonoids; D003102:Colloids; D044945:Proanthocyanidins; D012471:Salivary Proteins and Peptides; D013634:Tannins; C017674:procyanidin; D002392:Catechin