title: Noncovalent cross-linking of casein by epigallocatechin gallate characterized by single molecule force microscopy.
abstract: Interaction of the tea polyphenol epigallocatechin gallate (EGCG) with beta-casein in milk affects the taste of tea and also affects the stability of the tea and the antioxidant ability of the EGCG. In addition, interaction of polyphenols with the chemically similar salivary proline-rich proteins is largely responsible for the astringency of tea and red wine. With the use of single molecule force microscopy, we demonstrate that the interaction of EGCG with a single casein molecule is multivalent and leads to reduction in the persistence length of casein as calculated using the wormlike chain model and a reduction in its radius of gyration. The extra force required to stretch casein in the presence of EGCG is largely entropic, suggesting that multivalent hydrophobic interactions cause a compaction of the casein micelle.
authors.affiliation: Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, United Kingdom.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Jöbstl
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Howse
authors.forename: J Patrick A
authors.initials: JP
authors.lastname: Fairclough
authors.forename: Mike P
authors.initials: MP
authors.lastname: Williamson
mesh_terms: D002364:Caseins / Q000737:chemistry*; D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003432:Cross-Linking Reagents; D057927:Hydrophobic and Hydrophilic Interactions; D008853:Microscopy / Q000379:methods; D008958:Models, Molecular; D010766:Phosphorylation; D013816:Thermodynamics
chemical_list: D002364:Caseins; D003432:Cross-Linking Reagents; D002392:Catechin; C045651:epigallocatechin gallate