title: Modeling procyanidin self-association processes and understanding their micellar organization: a study by diffusion NMR and molecular mechanics.
abstract: The colloidal behavior of eight synthetic procyanidins (three monomers, four dimers, and a trimer) has been investigated in water or in a winelike medium using DOSY NMR spectroscopy and molecular dynamics simulations. Different behavior was observed for monomers and oligomers. Monomers self-associate with a high affinity constant (37-53 M(-1)) to form micelles at low cmc (critical micelle concentration) values (1-5 g.L(-1)). These micelles undergo a time-dependent coalescence process to form hazes and precipitates. As for dimers and the trimer, self-association also occurs but with a lower affinity (approximately 6 M(-1)) and at higher cmc values (10-20 g.L(-1)) to form small micelles (<5 nm) that remain stable throughout the experiment. The presence of 10% ethanol does not significantly affect the self-association constant for monomers and oligomers but increases their cmc values by approximately 50% and decreases the micelle size by a factor 2. However, the presence of 20 mM NaCl appears to negate the effect of ethanol. This study helps to clarify the role of procyanidin monomers versus oligomers in wine turbidity and demonstrates that procyanidin oligomers are fully available to interact with saliva proteins.
authors.affiliation: Institut des Sciences Moléculaires, UMR 5255 CNRS - Universite Bordeaux 1, Talence, France. i.pianet@ism.u-bordeaux1.fr
authors.forename: Isabelle
authors.initials: I
authors.lastname: Pianet
authors.forename: Yann
authors.initials: Y
authors.lastname: André
authors.forename: Marie-Agnès
authors.initials: MA
authors.lastname: Ducasse
authors.forename: Isabelle
authors.initials: I
authors.lastname: Tarascou
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Lartigue
authors.forename: Noël
authors.initials: N
authors.lastname: Pinaud
authors.forename: Eric
authors.initials: E
authors.lastname: Fouquet
authors.forename: Erick J
authors.initials: EJ
authors.lastname: Dufourc
authors.forename: Michel
authors.initials: M
authors.lastname: Laguerre