title: Beta-lactoglobulin/folic acid complexes: formation, characterization, and biological implication.
abstract: Beta-lactoglobulin (beta-LG), the major whey protein in bovine milk, binds to a wide range of compounds. Folic acid (FA) is a synthetic form of the B group vitamin known as folates, which are essential cofactors for a variety of physiological processes. The interaction of beta-LG with FA was studied using fluorescence spectroscopy to determine the FA binding constant and mode and the influence of the protein on FA photodegradation. At < or = 20 microM FA, which may be the critical self-association concentration, the binding constant and number are 2.0 (+/-0.6) x 10(6) M(-1) and 1.30 (+/-0.03) when excited at 280 nm and 4.3 (+/-2.2) x 10(5) M(-1) and 1.17 (+/-0.04) at 295 nm, as determined by protein intrinsic fluorescence. FA binds to the surface of beta-LG, possibly in the groove between the alpha-helix and the beta-barrel. Fluorescence analysis of the pterin portion of FA shows that complexation with beta-LG improves FA photostability. It is suggested that beta-LG complexes could be used as an effective carrier of FA in functional foods.
authors.affiliation: Institut de recherche sur les nutraceutiques et les aliments fonctionnels (INAF/STELA), Université Laval, Québec, QC, Canada.
authors.forename: Li
authors.initials: L
authors.lastname: Liang
authors.forename: Muriel
authors.initials: M
authors.lastname: Subirade
mesh_terms: D000818:Animals; D002417:Cattle; D005492:Folic Acid / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry*; D010782:Photolysis; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence
chemical_list: D007782:Lactoglobulins; D005492:Folic Acid