大豆分离蛋白与染料木素共价交联对蛋白表征和结构的影响

探究大豆分离蛋白和染料木素的共价交联对蛋白表征和结构的影响。制备大豆分离蛋白与不同质量浓度染料木素（0、1.2、1.5、2.0 mg/mL）的共价复合物，通过探究粒径、Zeta电位、浊度、表面疏水性分析蛋白体系的表征变化，并采用紫外分光光度计、荧光分光光度计、傅里叶变换红外光谱仪分析蛋白体系的结构变化。结果表明：大豆分离蛋白与染料木素共价复合后，蛋白的中位径由135.6 μm最低减小至98.0 μm，Zeta电位绝对值由15.0 mV最高增大至21.4 mV，表面疏水性由216.0最低减小至115.5，总巯基含量由31.5 μmol/g最低减小至20.4 μmol/g。与对照组相比，共价复合物的浊度增加，并且实验组中SPI-Ge-1.2组低于SPI-Ge-1.5组和SPI-Ge-2.0组。光谱分析表明染料木素对大豆分离蛋白有猝灭效果，二者共价交联后蛋白质的色氨酸与酪氨酸残基所处的微环境疏水性减少，蛋白质二级结构中α-螺旋含量增多、β-折叠含量减少、β-转角含量增多、无规卷曲含量减少，并且加入1.2 mg/mL的染料木素对大豆分离蛋白的表征特征和结构影响效果更好。本研究结果表明在大豆分离蛋白中加入染料木素后，二者的共价交联能够影响蛋白的表征与结构。

Effect of Covalent Crosslinking of Soybean Protein Isolate with Genistein on Protein Characterization and Structure

In order to explore the effects covalent crosslinking between soybean protein isolate (SPI) and genistein on protein characterization and structure, covalent complexes between SPI and genistein, prepared by adding different concentrations (0, 1.2, 1.5 and 2.0 mg/mL) of genistein to SPI solution, were characterized by measuring particle size, zeta potential, turbidity and surface hydrophobicity, and the structural changes of SPI were analyzed by using an ultraviolet spectrophotometer, a fluorescence spectrophotometer and a Fourier transform infrared spectrometer. The results showed that the median particle size of SPI declined from 135.6 to a minimum value of 98.0 μm, the absolute value of zeta potential increased from 15.0 mV to a maximum value of 21.4 mV, the surface hydrophobicity decreased from 216.0 to a minimum value of 115.5, and the total sulfhydryl group content decreased from 31.5 μmol/g to a minimum value of 20.4 μmol/g after covalent complexation with genistein. Compared with the control group, the turbidity of the covalent complexes increased, and the turbidity of the SPI-Ge-1.2 complex was lower than that of the SPI-Ge-1.5 and SPI-Ge-2.0 complexes. Spectral analysis showed that genistein had a quenching effect on SPI. After covalent cross-linking, the hydrophobicity of the microenvironments of tryptophan and tyrosine residues in SPI decreased, the contents of α-helix and β-turn increased, and the contents of β-sheet and random coil decreased. The addition of 1.2 mg/mL genistein had a better effect on the characterization and structure of SPI. The results indicated that the covalent cross-linking of genistein with SPI can affect the characterization and structure of the protein.