β-Lactoglobulin/Folic Acid Complexes: Formation, Characterization, and Biological Implication

摘要

β-Lactoglobulin (β-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 β-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 ≤20 μM FA, which may be the critical self-association concentration, the binding constant and number are 2.0 (±0.6) × 10~6 M~(-1) and 1.30 (±0.03) when excited at 280nm and 4.3 (±2.2) × 10~5 M~(-1) and 1.17 (±0.04) at 295 nm, as determined by protein intrinsic fluorescence. FA binds to the surface of β-LG, possibly in the groove between the α-helix and the β-barrel. Fluorescence analysis of the pterin portion of FA shows that complexation with β-LG improves FA photostability. It is suggested that β-LG complexes could be used as an effective carrier of FA in functional foods.