title: Identification of Structural Features of Condensed Tannins That Affect Protein Aggregation.
abstract: A diverse panel of condensed tannins was used to resolve the confounding effects of size and subunit composition seen previously in tannin-protein interactions. Turbidimetry revealed that size in terms of mean degree of polymerisation (mDP) or average molecular weight (amw) was the most important tannin parameter. The smallest tannin with the relatively largest effect on protein aggregation had an mDP of ~7. The average size was significantly correlated with aggregation of bovine serum albumin, BSA (mDP: r = -0.916; amw: r = -0.925; p<0.01; df = 27), and gelatin (mDP: r = -0.961; amw: r = -0.981; p<0.01; df = 12). The procyanidin/prodelphinidin and cis-/trans-flavan-3-ol ratios gave no significant correlations. Tryptophan fluorescence quenching indicated that procyanidins and cis-flavan-3-ol units contributed most to the tannin interactions on the BSA surface and in the hydrophobic binding pocket (r = 0.677; p<0.05; df = 9 and r = 0.887; p<0.01; df = 9, respectively). Circular dichroism revealed that higher proportions of prodelphinidins decreased the apparent α-helix content (r = -0.941; p<0.01; df = 5) and increased the apparent β-sheet content (r = 0.916; p<0.05; df = 5) of BSA.
authors.affiliation: School of Agriculture, Policy and Development; Chemistry and Biochemistry Laboratory, University of Reading, Reading, Berkshire, United Kingdom.
authors.forename: Honorata M
authors.initials: HM
authors.lastname: Ropiak
authors.affiliation: Independent Researcher, Bookham, Surrey, United Kingdom.
authors.forename: Peter
authors.initials: P
authors.lastname: Lachmann
authors.affiliation: School of Agriculture, Policy and Development; Chemistry and Biochemistry Laboratory, University of Reading, Reading, Berkshire, United Kingdom.
authors.forename: Aina
authors.initials: A
authors.lastname: Ramsay
authors.affiliation: School of Chemistry, Food and Pharmacy; University of Reading, Reading, Berkshire, United Kingdom.
authors.forename: Rebecca J
authors.initials: RJ
authors.lastname: Green
authors.affiliation: School of Agriculture, Policy and Development; Chemistry and Biochemistry Laboratory, University of Reading, Reading, Berkshire, United Kingdom.
authors.forename: Irene
authors.initials: I
authors.lastname: Mueller-Harvey
mesh_terms: D000872:Anthocyanins / Q000737:chemistry*; D044946:Biflavonoids / Q000737:chemistry*; D002392:Catechin / Q000737:chemistry*; D005419:Flavonoids / Q000737:chemistry*; D005780:Gelatin / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry; D044945:Proanthocyanidins / Q000737:chemistry*; D066329:Protein Aggregates; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012996:Solutions; D013634:Tannins / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry
chemical_list: D000872:Anthocyanins; D044946:Biflavonoids; D005419:Flavonoids; D010936:Plant Extracts; D044945:Proanthocyanidins; D066329:Protein Aggregates; D012996:Solutions; D013634:Tannins; D012710:Serum Albumin, Bovine; C404987:flavan-3-ol; C017674:procyanidin; D014364:Tryptophan; D002392:Catechin; D005780:Gelatin