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Interactions between flavan-3-ols and poly (L-proline) studied by isothermal titration calorimetry: Effect of the tannin structure

Abstract : Interactions of proline-rich proteins (PRPs) with flavan-3-ols was studied using poly(L-proline) as a model protein by means of isothermal titration calorimetry (ITC). Several parameters were varied: (i) the galloylation and B-ring trihydroxylation of the flavan-3-ols (catechin, epicatechin, epicatechin gallate, and epigallocatechin gallate) and (ii) the degree of polymerization (monomers were compared to a mixture of oligomers with average degree of polymerization of 3.85). Large differences were observed between the flavan-3-ol monomers: no enthalpy change was measured when catechin and epicatechin were titrated by poly(L-proline), whereas thermodynamic parameters were determined in the case of galloylated monomers and mixture of oligomers. Stoichiometry ranged from 1 oligomer bound for each 12 proline units to 1 galloylated monomer for each 8 or 10 proline units. Association constants were in the range of 10(4)-10(5) M-1, indicating a relatively high affinity of galloylated flavanols toward poly(L-proline), and the coexistence of both enthalpy- and entropy-driven phenomena was suggested. Finally, the binding of grape seed tannins to proteins was shown to be a cooperative process
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Submitted on : Sunday, May 31, 2020 - 12:58:43 PM
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Celine Poncet-Legrand, Catherine Gautier, Veronique Cheynier, Anne Imberty. Interactions between flavan-3-ols and poly (L-proline) studied by isothermal titration calorimetry: Effect of the tannin structure. Journal of Agricultural and Food Chemistry, American Chemical Society, 2007, 55 (22), pp.9235-9240. ⟨10.1021/jf071297o⟩. ⟨hal-02668511⟩

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