pH偏移诱导对大豆亲脂蛋白纳米颗粒及其解离缔合行为的影响

Effects of pH-shift induction on fabricated nanoparticles and dissociation-association of soy lipophilic protein

为探究pH偏移诱导对大豆亲脂蛋白自组装纳米颗粒及其亚基解离缔合行为的影响,将大豆亲脂蛋白在不同pH条件下进行偏移诱导处理后,采用马尔文激光粒度仪联合多光谱、热分析等技术研究pH偏移诱导大豆亲脂蛋白自组装纳米颗粒及其蛋白亚基解离缔合行为并进行表征。结果显示,pH偏移诱导过程中,大豆亲脂蛋白结构经历去折叠、亚基解离以及再聚集,约10 h后蛋白构象趋于稳定,最终使大豆亲脂蛋白表面分布更多的酪氨酸和色氨酸,从而呈现出松散三维构象。傅里叶红外光谱和圆二色谱分析结果显示,pH偏移诱导(10 h)改变了蛋白表面亲水性侧链并破坏了维系蛋白二级结构的氢键等作用力,引起α-螺旋结构解旋,β-折叠含量增加;热分析结果显示,在等电点处大豆亲脂蛋白具有最大的抗变性能力。pH偏移诱导过程中,大豆亲脂蛋白纳米颗粒发生自组装,形成形状较规则且尺寸均一的球体纳米颗粒,其分子形态由无序聚集状态向粒径分布均匀状态转变,在pH 4条件下诱导的大豆亲脂蛋白颗粒呈稳定的单分布体系,进而呈现出良好的分子柔性和乳化特性。

In order to explore the effect of pH-shift induction on the dissociation-association behavior of soybean lipophilic protein(SLP)and the self-assembled nanoparticles,the SLP was treated by pH-shift inducted and the dissociation-association behavior of SLP and its self-assembled nanoparticles induced were characterized by thermal analysis and dynamic light scattering techniques.The results showed that the structure of SLP protein experienced unfolding,subunit dissociation and reaggregation during pH-shift induction.After about 10 h,more tyrosine and tryptophan were distributed on the surface of SLP with a stable and a loose three-dimensional conformation.The results of Fourier transform infrared spectroscopy and circular dichroism spectroscopy showed that pH-shift induction(10 h)changed the hydrophilic side chains on the protein surface and destroyed the hydrogen bonds and other forces acting on the secondary structure of the protein.Besides,it also caused theα-helix structure change to spin and increased theβ-sheet content.The thermal analysis results showed that SLP had the maximum anti-degeneration ability at the isoelectric point.During the process of pH-shift induction,SLP nanoparticles self-assembled to form spherical nanoparticles with regular shape and uniform size,whose molecular morphology changed from disordered aggregation state to uniform particle size distribution.The SLP nanoparticles induced at pH 4 showed a stable single distribution system,and then exhibited good molecular flexibility and emulsifying properties.