离子强度对大豆分离蛋白结构及表面疏水性的影响

The effect of ionic strength on structure and surface hydrophobicity of soy protein isolate

旨在采用生物化学和光谱学方法及手段,从蛋白质分子空间构象和溶液性质角度,探讨离子强度对大豆分离蛋白结构及表面疏水性的影响机制。研究表明：大豆分离蛋白表面疏水性在等电点两侧呈现显著下降趋势,而随着离子强度的增大大豆分离蛋白表现出＂盐析＂现象,表面疏水性总体上呈现增大趋势;大豆分离蛋白的λ_（max）整体上随离子强度的增加而增大,表明色氨酸残基趋向于亲水性微环境。在离子强度从0.1~0.9 mol/L时,α-螺旋结构含量增大,而β-折叠结构含量有所降低,β-转角结构含量随离子强度略有降低,相关性分析表明无规卷曲结构与表面疏水值之间呈现显著的正相关（r=0.81,p〈0.05）。随着离子强度的增大,大豆分离蛋白分子平均粒径总体呈现增大的变化趋势,ζ-电位绝对值总体呈现降低趋势,并与表面疏水性之间亦表现出显著负相关（r=-0.86,p〈0.05）。大豆分离蛋白空间构象与表面疏水性之间的构效关系,可以为大豆精深加工及高值化应用提供理论依据。

Surface hydrophobicity of proteins depends not only on source of protein,conditions and method of processing,but aslo on physicochemical properties and structure characteristics. In the viewpoint of protein molecular conformation and solution properties,this study focused on ionic strength on structure and surface hydrophobicity of soy protein isolate with biochemical,spectroscopic methods,to definite the relationship between the spatial conformation and surface hydrophobicity of soybean protein isolate. The main results were as follows：surface hydrophobicity of soy protein isolate significantly decreases at both sides of isoelectric point. Soy protein isolate showed ＂ salting- out ＂ phenomenon, surface hydrophobicity increased with the increasing ionic strength. The increasing λ_（max） of soybean protein isolate with ionic strength suggested that tryptophan residues tend to hydrophilic microenvironment. As ionic strength from 0.1 mol/L to 0.9 mol/L,the content of α-helix structure increased while the percentage of β-sheet structure decreased to 35.19%,the content of β-turn structure showed a slight reduction. Random coil structure showed a significant positive correlation with surface hydrophobicity value（r=0.81,p0.05） from correlation analysis. The average particle size of protein molecular generally increased with ionic strength,the absolute value of zeta potential declined in general,and also showed a significant negative correlation with surface hydrophobicity（r=-0.86,p0.05）. This study provided theoretical basis for the deeper processing of soybean and application for high value.