花生分离蛋白氧化过程中的结构变化

Structural evaluation of peanut protein isolates during oxidation by FTIR

利用2,2-盐酸脒基丙烷(AAPH)在有氧条件下热分解产生的烷过氧自由基(ROO·),对花生分离蛋白进行不同程度的氧化修饰,采用傅里叶红外变换光谱,结合去卷积和曲线拟合技术,研究花生分离蛋白氧化过程中的二级结构变化。结果表明,经去卷积后花生分离蛋白红外光谱酰胺I带共分出10个峰,表征聚集体形成的1 618,1 682 cm-1的吸收值在氧化过程中升高,表明在氧化过程中形成了蛋白聚集体。利用曲线拟合对酰胺I带进行定量分析,结果表明,当AAPH浓度小于3.00 mmol/L时,β-折叠和无规则卷曲含量升高,而β-转角和α-螺旋含量下降;在高氧化浓度(5.00,10.00 mmol/L)下,花生分离蛋白发生多肽链的断裂,进而影响其二级结构的变化。AAPH的浓度不同,花生分离蛋白之间的分子相互作用强度不同。在花生分离蛋白聚集体形成中,氢键和疏水相互作用发挥着重要作用。

Peanut protein isolates（PPI） was oxidized by peroxyl radicals derived from 2,2 ＇-azobis（2-amidinopropane） dihydrochloride（AAPH）and the secondary structure of oxidized PPI were evaluated.Structural changes of PPI were elucidated using Fourier transform infrared spectroscopy（FTIR）.Fourier deconvolution combined with iterative curve fitting was used to analyze the amide I of FTIR.After deconvolved amide I FTIR bands,ten major bands associated with conformation of proteins were distinctly observed.Changes in the bands at 1 618 cm-1and 1 682 cm-1,which arise from the aggregated intermolecular β-sheets,indicated that protein aggregation occurred during PPI oxidation.Quantitative analysis was obtained by iterative curve fitting.The results showed that there was an increase in β-sheet structure and random structures accompanied by a decrease in turns and alpha helix,with the increase of oxidizing agent（AAPH 3.00 mmol/L）.Higher level oxidation（5.00 and 10.00 mmol / L） would induce fragmentation through direct breakage of peptide bonds,resulted in changes in the secondary structures.The hydrogen bonds and hydrophobic interactions played an important role in the formation of PPI aggregates.