Herein, the effects of ultrasound-assisted L-histidine (L-His) on the physicochemical properties and conformation of soybean protein isolate (SPI) were investigated. Particle size, zeta potential, turbidity, and solubility were used to evaluate protein aggregation, and the relationship between structural and functional changes of the proteins was characterized using spectral analysis, surface hydrophobicity, emulsification, and antioxidant properties. After ultrasound-assisted L-His treatment, SPI exhibited a smaller particle size, higher solubility, and more homogeneous micromorphology owing to the decrease in alpha-helix content and subsequent increases in zeta potential and active sulfhydryl content. In addition, spectral analysis showed that L-His and SPI could form a complex, which changed the microenvironment of the amino acid residues in SPI, thus improving its emulsification and antioxidant properties. At the concentration of L-His was 0.3 % w/w, the nanocomplex had a smaller particle size (140.03 nm), higher ζ-potential (–23.63 mV), and higher emulsification stability (22.48 min).

中文翻译：

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L-组氨酸超声辅助修饰大豆分离蛋白：结构与功能之间的关系


本文研究了超声辅助 L-组氨酸 (L-His) 对大豆分离蛋白 (SPI) 理化性质和构象的影响。使用粒径、zeta 电位、浊度和溶解度来评估蛋白质聚集，并使用光谱分析、表面疏水性、乳化和抗氧化特性来表征蛋白质结构和功能变化之间的关系。经过超声辅助 L-His 处理后，由于 α-螺旋含量减少以及随后 zeta 电位和活性巯基含量增加，SPI 表现出更小的粒径、更高的溶解度和更均匀的微观形态。此外，光谱分析表明L-His与SPI可以形成复合物，改变了SPI中氨基酸残基的微环境，从而提高了其乳化和抗氧化性能。当 L-His 浓度为 0.3% w/w 时，纳米复合物具有较小的粒径（140.03 nm）、较高的 z 电位（–23.63 mV）和较高的乳化稳定性（22.48 分钟）。