酸性条件下花生分离蛋白亚基结构的变化规律

Structural Variations in the Subunits of Peanut Protein Isolates under Acidic Conditions

摘要:

本文通过SDS-PAGE凝胶电泳、Zeta电位、溶解性、内源荧光光谱以及粒径的测定分析，探讨了酸性条件下花生分离蛋白亚基结构的变化规律。电泳分析表明，当pH<3.5时，部分亚基酸解产生约33 ku的新条带，18 ku条带亮度增加。亚基的酸解受时间和离子强度的影响。花生分离蛋白亚基在常温pH 2.5的条件下处理10 min后开始酸解，且随着时间的延长高分子量的亚基逐渐减少；在离子强度0~0.1 mmol/L时酸解程度较大，当离子强度大于0.2 mmol/L时，酸解作用被抑制。进一步研究表明，在pH 2.0~2.5间，花生分离蛋白结构较为伸展，内部基团暴露，溶解性较高，荧光光谱最大吸收波长比中性条件时红移约13 nm；当pH进一步降低时，Zeta电位较低，花生分离蛋白形成大分子量的可溶性聚集体，荧光光谱最大吸收波长蓝移至335.27 nm。

Abstract:

Structural variations in the subunits of peanut protein isolates under acidic conditions were investigated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), zeta potential, solubility, endogenous fluorescence spectroscopy, and particle size distribution analyses. The electrophoresis analysis indicated that when the pH value was <3.5, a portion of the subunits unfolded, a new 33 ku band was produced, and the intensity of the 18 ku band increased. The acid-hydrolysis of the subunits was affected by time and ionic strength. The peanut protein isolate subunits were subjected to acid-hydrolysis at pH 2.5 after 10 min at room temperature, and the amount of high molecular weight subunits decreased over time. When the ionic strength ranged from 0~0.1 mmol/L, there was a higher degree of acid-hydrolysis, which was inhibited when the ionic strength was above 0.2 mmol/L. Moreover, at pH values ranging from 2.0~2.5, the peanut protein isolate unfolded, interior groups were exposed, solubility was relatively high, and the maximum emission wavelength in the fluorescence spectra was red-shifted by 13.47 nm as compared to that under neutral conditions. When the pH was further decreased, the zeta potential was relatively low, peanut protein isolates formed high molecular weight soluble aggregates, and the maximum emission wavelength in the fluorescence spectra was blue-shifted to 335.27 nm.