Binding to Bovine Serum Albumin Protects β-Carotene against Oxidative Degradation

• DOI: 10.1021/acs.jafc.6b02436
• Publication Date: 2016-07-11T22:47:12Z
• Authors: Hui-Ting Chang; Hong Cheng; Rui-Min Han; Jian-Ping Zhang; Leif H. Skibsted
• Keywords: Binding constant; Bovine serum albumin; Flash photolysis

Binding to bovine serum albumin (BSA) was found protect β-carotene (β-Car) dissolved in air-saturated phosphate buffer solution/tetrahydrofuran (9:1, v/v) efficiently against photobleaching resulting from laser flash excitation at 532 nm. From dependence of the relative yield upon BSA concentration, an association constant Ka = 4.67 × 10(5) L mol(-1) for β-Car binding determined 25 °C. Transient absorption spectroscopy confirmed less bleaching on microsecond time scale presence BSA, while kinetics triplet-state unaffected by oxygen. The protection this type reaction seems accordingly depend dissipation energy excited state into protein matrix. Static quenching fluorescence had a Stern-Volmer Ksv 2.67 10(4) mol(-1), with ΔH 17 kJ and ΔS 142 J K(-1) Quenching tryptophan (Trp) suggests involvement Trp through hydrophobic interaction, lower value compared constant, Ka, may indicate aggregates. Bound increased random coil fraction expense α-helix, as shown circular dichroism, affecting configuration, Raman spectroscopy.