Liu Jun, Tu Zongcai, Shao Yan-Hong, Wang Hui, Liu Guang-Xian, Sha Xiao-Mei, Zhang Lu, Yang Ping
College of Chemistry and Chemical Engineering, College of Life Science, Jiangxi Normal University , Nanchang, Jiangxi 330022, China.
State Key Laboratory of Food Science and Technology, Nanchang University , Nanchang, Jiangxi 330047, China.
J Agric Food Chem. 2017 Nov 29;65(47):10317-10324. doi: 10.1021/acs.jafc.7b03920. Epub 2017 Nov 13.
High-resolution mass spectrometry was performed to investigate the relationship between bovine α-lactalbumin (α-LA) subjected to ultrasonication and glycation treatment with respect to antioxidant activity. After α-LA was pretreated by ultrasonication combined with glycation, the treated α-LA showed low intrinsic fluorescence emission and high antioxidant activity at increased ultrasonic power levels. Prior to ultrasonic pretreatment, three glycated sites were identified, whereas the number of glycation sites was increased to four, four, five, and six after ultrasonic power at 60, 90, 120, and 150 W/cm, respectively, for 15 min. Thus, no obvious difference was found among the glycation sites at the ultrasonic power of 60 and 90 W/cm. The average degree of substitution per peptide molecule of α-LA was used to evaluate the glycation level per glycation site. All the samples pretreated by ultrasonication exhibited a higher glycation level compared with the untreated samples. Ultrasonic power at 150 W/cm showed the most highly enhanced glycation extent and antioxidant activity. Therefore, the intensified glycation extent and the conformational changes of protein were responsible for the increase of antioxidant activity of α-LA. Moreover, high-resolution mass spectrometry is an efficient technique to understand the mechanism of the improved antioxidant activity.
采用高分辨率质谱法研究了经超声处理和糖基化处理的牛α-乳白蛋白（α-LA）与抗氧化活性之间的关系。在α-LA经超声处理结合糖基化预处理后，在较高超声功率水平下，处理后的α-LA表现出较低的固有荧光发射和较高的抗氧化活性。在超声预处理之前，鉴定出三个糖基化位点，而在分别以60、90、120和150 W/cm的超声功率处理15分钟后，糖基化位点的数量分别增加到四个、四个、五个和六个。因此，在60和90 W/cm的超声功率下，糖基化位点之间没有明显差异。用α-LA每个肽分子的平均取代度来评估每个糖基化位点的糖基化水平。与未处理的样品相比，所有经超声处理的样品都表现出更高的糖基化水平。150 W/cm的超声功率显示糖基化程度和抗氧化活性增强最为显著。因此，糖基化程度的增强和蛋白质的构象变化是α-LA抗氧化活性增加的原因。此外，高分辨率质谱法是了解抗氧化活性提高机制的一种有效技术。
