分子动力学结合拉曼光谱评价乳液界面蛋白结构变化

Structural Changes of Interfacial Proteins in Emulsions Evaluated by Molecular Dynamics Combined with Raman Spectroscopy

使用质量分数1.5%罗非鱼肌原纤维蛋白(myofibrillar protein,MP)和玉米油(0%、10%、68%、70%,V/V)制备乳液体系,并通过分子动力学(molecular dynamics,MD)结合拉曼光谱技术探究乳液界面蛋白结构的变化。MD模拟显示,蛋白吸附到不同油相体积分数的乳液界面上,肌球蛋白的空间构象改变,二级结构中均含有48%左右α-螺旋结构,且吸附到界面后结构相对稳定。肌球蛋白空间构象改变伴随溶剂可及表面积增大,疏水相互作用增强,使乳液呈稳定状态。拉曼光谱与MD模拟具有相似的二级结构变化。此外,拉曼光谱结果还显示,色氨酸和酪氨酸残基暴露于蛋白质表面,参与氢键形成和疏水相互作用,有利于乳液体系保持稳定。综上,MP主要通过改变界面蛋白质空间构象和侧链基团微环境,促进蛋白质之间的氢键和疏水相互作用,使MP在油-水界面形成紧密的界面膜,有利于提高乳液稳定性。

In this study,1.5%(m/m)tilapia myofibrillar protein(MP)and corn oil(0%,10%,68%or 70%,V/V)were used to prepare emulsions.Molecular dynamics(MD)combined with Raman spectroscopy was used to investigate the structural changes of MP adsorbed at the emulsion interface.MD simulation showed that the spatial conformation of myosin was changed when the protein adsorbed onto the interface of emulsions with different proportions of oil phase;the secondary structure contained about 48%α-helix,and the structure remained relatively stable after the protein adsorbed onto the interface.The change of myosin spatial conformation was accompanied by the increase of solvent accessible surface area(SASA)and the enhancement of hydrophobic interaction,which made the emulsion stable.Raman spectra showed secondary structural changes similar to those of MD.In addition,Raman spectroscopy results showed that tryptophan(Trp)and tyrosine(Tyr)residues were exposed on the protein surface and participated in hydrogen bond formation and hydrophobic interaction,which was conducive to the stability of the emulsion system.In conclusion,changes in the spatial conformation and the microenvironment of side chain groups of MP adsorbed at the oil/water interface of emulsions can promote the hydrogen bond and hydrophobic interaction between protein molecules,and consequently the formation of a tight interfacial film at the oil/water interface,which is conducive to improving the stability of emulsions.