分子动力学模拟解析脉冲电场对类PSE鸡肉肌球蛋白凝胶特性作用规律

Effects of Pulsed Electric Field on Gelation Properties of PSE-Like Chicken Myosin:A Molecular Dynamics Simulation Analysis

【目的】以类PSE鸡肉肌原纤维蛋白为研究对象,通过分子动力学模拟技术研究脉冲电场处理对其凝胶特性和构象修饰的影响,并对凝胶特性改变的潜在机制进行阐述,以此拓宽这种新兴食品加工技术的工业应用,为禽类加工方向提高异常肉制品的经济效益提供一种新的方法。【方法】本试验选取类PSE鸡肉为原料并提取其肌原纤维蛋白,对比8、18和28 kV·cm^(-1)电场强度下脉冲电场(脉冲电场频率为800 Hz,占空比47%)处理及非脉冲电场处理的类PSE鸡肉肌原纤维蛋白不稳定动力学指数、流变学特性及通过分子动力学技术建立电场强度18 kV·cm^(-1)的脉冲电场模拟体系,通过收集模拟过程中的均方根偏差(RMSD)、均方根波动(RMSF)和对蛋白质总体构象的观察的变化来阐明在该条件下脉冲电场处理对类PSE鸡肉肌原纤维蛋白分子构象动态变化的作用机制。研究脉冲电场作用对类PSE鸡肉肌原纤维蛋白构象稳定性、保水性、流变特性的影响。【结果】不同电场强度的脉冲电场处理后的类PSE鸡肉肌原纤维蛋白体系不稳定动力学曲线斜率更小,蛋白体系相较于未经处理的样品更加稳定。蛋白凝胶的保水性结果为18 kV·cm^(-1)(81.42%)>28 kV·cm^(-1)(79.46%)>8 kV·cm^(-1)(77.82%)>0 kV·cm^(-1)(76.15%),流变学特性研究表明储能模量(G′)和损耗模量(G″)的变化与保水性变化具有相同的趋势,且18 kV·cm^(-1)的脉冲电场处理显著提高了蛋白凝胶的G′和G″(P<0.05)。18 kV·cm^(-1)电场强度下进行30 ns的分子动力学模拟结果显示,多聚体蛋白模型在处理后显示出更高的RMSD值及更为显著的RMSF波动,体现为蛋白质分子二级结构发生解螺旋和解折叠,α-螺旋转变为无规则卷曲,蛋白质分子多肽链展开,氨基酸残基暴露,同时蛋白质分子表现出更高的柔韧性。蛋白质-蛋白质和蛋白质-水之间的相互作用,如静电相互作用、氢键、二硫键、疏水相互作用等发生改变。但电场强度继续增加至28 kV·cm^(-1)时,肌球蛋白因蛋白质间的相互作用增强而聚集使脉冲电场对蛋白质特性改善的作用降低。【结论】18 kV·cm^(-1)的脉冲电场处理改变了类PSE鸡肉肌原纤维蛋白原有的空间结构,疏水基团的外露和氢键的形成增强蛋白质与水分子的结合及蛋白质分子间的相互作用从而提高类PSE鸡肉肌球蛋白凝胶的稳定性和流变特性,表现出更优的凝胶保水性和弹性网络结构。

【Objective】In the present study,the effects of pulsed electric field(PEF)on pale soft exudative-like(PSE-like)chicken myofibrillar protein gel properties and conformational modification were investigated by molecular dynamics simulation.The potential mechanism of gel properties change was explored,so as to broaden the industrial application of this emerging food processing technology and to provide a novel method for enhancing abnormal meat products economic benefit in poultry processing.【Method】Myofibrillar protein was extracted from PSE-like chicken.Effect of PEF under 8,18 and 28 kV·cm^(-1)electric field intensity(800 Hz,duty cycle 47%)were compared with untreated samples of PSE-like chicken myofibrillar for turbiscan stability index(TSI)and rheological properties,and the PEF simulation system of 18 k V·cm^(-1)electric field strength was established by molecular dynamics simulation technology.The root mean square deviation(RMSD),root mean square fluctuation(RMSF)and the overall conformational changes of proteins were collected to explore the mechanism of PEF treatment on the molecular conformational changes of myofibrillar proteins in PSE-like chicken,and the effects of PEF on the conformational stability,water holding capacity(WHC)and rheological properties of myofibrillar protein extracted from PSE-like chicken were also evaluated.【Result】The TSI of the PSE-like chicken myofibrillar protein system treated by PEF with various field strengths had a smaller slope,which indicated that the protein system was more stable than the untreated sample.The results of WHC of protein gel were 18kV·cm^(-1)(81.42%)>28 kV·cm^(-1)(79.46%)>8 kV·cm^(-1)(77.82%)>0 kV·cm^(-1)(76.15%).The rheological properties demonstrated that the changes of storage modulus(G’)and loss modulus(G")had the same trend as that of WHC,and the treatment of 18 kV·cm^(-1)significantly improved the G’and G"of myofibrillar protein gel(P<0.05).The molecular dynamics simulation result of 30 ns under18 kV·cm^(-1)PEF revealed the polymer protein model acted higher RMSD value and more obvious RMSF fluctuation after treatment,which reflected that the secondary structure of protein molecule was uncoiled and unfolded,α-helix was transformed into irregular crimp,protein polypeptide chain was expanded,amino acid residues were exposed,and protein molecules displayed higher flexibility.Interactions of protein-protein and protein-water have been modified,such as electrostatic interaction,hydrogen bond,disulfide bond,hydrophobic interaction.However,when the electric field intensity increased to 28 kV·cm^(-1),myosin aggregated due to the enhancement of protein-protein interaction,which reduced the effect of PEF on protein property.【Conclusion】The 18 kV·cm^(-1)PEF changed the inherent spatial structure of PSE-like chicken myofibrillar protein,the exposure of hydrophobic groups and the formation of hydrogen bonds enhanced the binding of protein and water molecules and the interaction between protein molecules,thus improving the stability and rheological properties of PSE-like chicken myosin gel,which contribute to better gel WHC and elastic network structure.