Raman Spectroscopy Study Structural Changes in Black Bean Protein Isolate upon Ultrasonic-Treatment
YANG Yong1，2, WANG Zhong-jiang2, BI Shuang2, SUI Xiao-nan2, QI Bao-kun2, LI Yang2*, JIANG Lian-zhou2*
1. College of Food Science，Northeast Agricultural University, Harbin 150030，China 2. Key Laboratory of Processing Agricultural Products of Heilongjiang Province, College of Food and Bioengineering, Qiqihar University, Qiqihar 161006，China
Abstract：This article focused on the assessment of the potential of Raman spectroscopy for the determination of structural changes in black-bean protein isolate (BBPI) dispersions with low-frequency (20 kHz) ultrasonication applied at various powers (150, 300 or 450 W) and for different durations (12 or 24 min). It also reported on differential scanning calorimetry analyses. A decrease in TD at low- and medium-power ultrasonication confirmed these ultrasonication treatment disrupted internal hydrophobic interactions of protein molecules and broke up unstable aggregates to smaller soluble protein aggregates, while an increase in TD at high-power was attributed to repolymerization of aggregates. Raman spectroscopy analysis revealed a decrease in the α-helix proportion and an increase in β-sheets after ultrasonic treatment except Sample E (300 W, 24 min). Transformation of aggregation results in a reconstruction in secondary structure of BBPI, especially in β-sheet structure. Ultrasonic-treatment induced a decrease in the normalized intensity of the Raman band near 760 cm-1 which indicated that Tryptophan residues tended to expose and also indicated protein partially unfolding. No significant difference was found in Tyr doublet ratios between unheated and ultrasound-treated BBPI indicated that ultrasound did not change the microenvironment around tyrosyl residues. While the intensity of 1 450 cm-1 band increased with increasing ultrasonic intensity and treatment time, and then decreased with further increase in power and treatment time. In general, the formation of aggregation transferred g-g-t conformation to t-g-t conformation. Though some mechanism of aggregation-repolymerization of BBPI remains to be clearly defined, Raman spectroscopy provide a feasible tool to study the structural changes of BBPI prepared under different ultrasonic conditions, give a new perspective to elucidation of protein structure.
Key words：Ultrasonic-treatment;black bean protein isolate;structure;Raman spectroscopy
杨 勇1,2，王中江2，毕 爽2，隋晓楠2，齐宝坤2，李 杨2*，江连洲2* . 超声处理黑豆蛋白结构变化的拉曼光谱分析 [J]. 光谱学与光谱分析, 2016, 36(07): 2318-2324.
YANG Yong1，2, WANG Zhong-jiang2, BI Shuang2, SUI Xiao-nan2, QI Bao-kun2, LI Yang2*, JIANG Lian-zhou2*. Raman Spectroscopy Study Structural Changes in Black Bean Protein Isolate upon Ultrasonic-Treatment. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2016, 36(07): 2318-2324.
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