制备方法对大豆7S和11S球蛋白的结构和热稳定性影响

Effects of Preparing Methods on the Structure and Thermal Stability of Soybean 7S and 11S Globulin

大豆蛋白的主要组分是β-伴大豆球蛋白(7S)和大豆球蛋白(11S),加工方法不同将会对其结构与热稳定性产生重要的影响。文章采用扫描电镜(SEM)、X-射线衍射(XRD)、傅里叶红外光谱(FTIR)、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)及差示热量扫描仪(DSC)等方法对比研究了等电点沉淀法和等电点沉淀结合含促溶剂的反胶束法制备的大豆7S和11S球蛋白结构和热稳定性。结果表明,SEM图像显示2种提取方法制备的7S和11S球蛋白的整体微观结构及蛋白表面都存在显著差异(P<0.05);XRD检测发现2种方法制备的球蛋白骨架结构无显著差异(P>0.05),但含促溶剂的反胶束法可以修饰蛋白的无定形结构;FTIR分析发现含促溶剂的反胶束制备蛋白中β-转角含量较高,β-折叠含量较少;SDS-PAGE图谱显示含促溶剂的反胶束法更能保护蛋白分子的亚基结构,蛋白的纯度也更高;DSC结果展示含促溶剂的反胶束法制备的7S和11S球蛋白的热变性温度显著高于等电点沉淀法(P<0.05)。以上结果表明,等电点沉淀结合含促溶剂的反胶束法改变了7S和11S球蛋白结构和热稳定性,提取效果总体优于等电点沉淀法。

The main components of soybean protein are β-glucoglobulin(7S) and globulin(11S). Different processing methods will have an important impact on its structure and thermal stability. The scanning electron microscopy(SEM), X-ray diffraction(XRD), Fourier infrared spectroscopy(FTIR), SDS-PAGE and differential calorimetry(DSC) were applied to contrast and analyze the structure and thermal stability of 7S and 11S globulins obtained through the isoelectric point precipitation and the isoelectric point precipitation method combined with reverse micelle method containing chaotropic agents. SEM results showed that the surface microstructure of 7S and 11S globulins obtained through the two preparation methods were significantly different(P<0.05);XRD images found that the skeleton structure of globulins was not significantly different(P>0.05), but the reverse micelles with chaotropic agents could modify the amorphous structure of the protein;FTIR analysis found that the β-turn content of protein obtained by the reverse micelles with chaotropic agents was higher, β-sheet content was lower;SDS-PAGE electrophoresis pattern showed that the reverse micelles with chaotropic agents could better protect the subunit structure of the protein, and the purity of the protein also was higher;DSC results showed that the thermal denaturation temperature of the 7S and 11S globulins prepared by the reverse micelles with chaotropic agents was significantly higher than that of the isoelectric point precipitation method(P<0.05). The above results showed that the isoelectric precipitation combined with the reverse micelle method containing prosolvent changed the structure and thermal stability of 7S and 11S globulins, and the extraction effect was better than that of isoelectric precipitation.