Binding to Bovine Serum Albumin Protects β-Carotene against Oxidative Degradation
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- 作者：Hui-Ting Chang ; Hong Cheng ; Rui-Min Han ; Jian-Ping Zhang ; Leif H. Skibsted
- 刊名：Journal of Agricultural and Food Chemistry
- 出版年：2016
- 出版时间：July 27, 2016
- 年：2016
- 卷：64
- 期：29
- 页码：5951-5957
- 全文大小：436K
- 年卷期：0
- ISSN：1520-5118
文摘
Binding to bovine serum albumin (BSA) was found to 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 photobleaching yield upon the BSA concentration, an association constant of Ka = 4.67 × 105 L mol–1 for β-Car binding to BSA was determined at 25 °C. Transient absorption spectroscopy confirmed less bleaching of β-Car on the microsecond time scale in the presence of BSA, while kinetics of triplet-state β-Car was unaffected by the presence of oxygen. The protection of β-Car against this type of reaction seems accordingly to depend upon dissipation of excitation energy from an excited state into the protein matrix. Static quenching of BSA fluorescence by β-Car had a Stern–Volmer constant of Ksv = 2.67 × 104 L mol–1, with ΔH = 17 kJ mol–1 and ΔS = 142 J mol–1 K–1 at 25 °C. Quenching of tryptophan (Trp) fluorescence by β-Car suggests involvement of Trp in binding of β-Car to BSA through hydrophobic interaction, while the lower value for the Stern–Volmer constant Ksv compared to the binding constant, Ka, may indicate involvement of β-Car aggregates. Bound β-Car increased the random coil fraction of BSA at the expense of α-helix, as shown by circular dichroism, affecting the β-Car configuration, as shown by Raman spectroscopy.