title: Protein Precipitation Behavior of Condensed Tannins from Lotus pedunculatus and Trifolium repens with Different Mean Degrees of Polymerization.
abstract: The precipitation of bovine serum albumin (BSA), lysozyme (LYS), and alfalfa leaf protein (ALF) by two large- and two medium-sized condensed tannin (CT) fractions of similar flavan-3-ol subunit composition is described. CT fractions isolated from white clover flowers and big trefoil leaves exhibited high-purity profiles by 1D/2D NMR and purities >90% (determined by thiolysis). At pH 6.5, large CTs with a mean degree of polymerization (mDP) of ∼18 exhibited similar protein precipitation behaviors and were significantly more effective than medium CTs (mDP ∼9). Medium CTs exhibited similar capacities to precipitate ALF or BSA, but showed small but significant differences in their capacity to precipitate LYS. All CTs precipitated ALF more effectively than BSA or LYS. Aggregation of CT-protein complexes likely aided precipitation of ALF and BSA, but not LYS. This study, one of the first to use CTs of confirmed high purity, demonstrates that the mDP of CTs influences protein precipitation efficacy.
authors.affiliation: U.S. Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture , 1925 Linden Drive, Madison, Wisconsin 53706, United States.
authors.forename: Wayne E
authors.initials: WE
authors.lastname: Zeller
authors.affiliation: U.S. Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture , 1925 Linden Drive, Madison, Wisconsin 53706, United States.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Sullivan
authors.affiliation: Chemistry and Biochemistry Laboratory, Food Production and Quality Division, School of Agriculture, Policy and Development, University of Reading , P.O. Box 236, 1 Earley Gate, Reading RG6 6AT, United Kingdom.
authors.forename: Irene
authors.initials: I
authors.lastname: Mueller-Harvey
authors.affiliation: U.S. Dairy Forage Research Center, Agricultural Research Service, U.S. Department of Agriculture , 1925 Linden Drive, Madison, Wisconsin 53706, United States.
authors.forename: John H
authors.initials: JH
authors.lastname: Grabber
authors.affiliation: Chemistry and Biochemistry Laboratory, Food Production and Quality Division, School of Agriculture, Policy and Development, University of Reading , P.O. Box 236, 1 Earley Gate, Reading RG6 6AT, United Kingdom.
authors.forename: Aina
authors.initials: A
authors.lastname: Ramsay
authors.affiliation: Chemistry and Biochemistry Laboratory, Food Production and Quality Division, School of Agriculture, Policy and Development, University of Reading , P.O. Box 236, 1 Earley Gate, Reading RG6 6AT, United Kingdom.
authors.forename: Chris
authors.initials: C
authors.lastname: Drake
authors.affiliation: Chemistry and Biochemistry Laboratory, Food Production and Quality Division, School of Agriculture, Policy and Development, University of Reading , P.O. Box 236, 1 Earley Gate, Reading RG6 6AT, United Kingdom.
authors.forename: Ronald H
authors.initials: RH
authors.lastname: Brown
keywords: NMR; condensed tannin; nuclear magnetic resonance spectroscopy; proanthocyanidin; protein precipitation; tannin−protein complexes; thiolysis