不同离子强度下罗非鱼肌球蛋白热变性聚集研究

Study on the thermal denaturation and aggregation of tilapia myosin under different ionic strength conditions

以罗非鱼肉为原料,提取肌球蛋白,分析不同离子强度(1、50、150、300、600 mmol/L KCl)下热处理(40~80℃,1℃/min)对其浊度、溶解度、表面疏水性、α-螺旋含量及聚集体粒径的影响。结果显示,离子强度及热处理温度明显影响肌球蛋白的热变性聚集。在低离子强度(1~150 mmol/L KCl)下,肌球蛋白聚集成纤丝,溶解性差,热处理后分子聚集沉淀,溶解度和α-螺旋含量减小(p<0.05),体系热稳定性差;在高离子强度(300~600 mmol/L KCl)下,肌球蛋白分子解离成单体,溶液澄清,当热处理温度高于50℃时,肌球蛋白溶解度下降,表面疏水性增加,α-螺旋含量显著减小(p<0.05),但分子聚集不明显。总体分析,高盐离子的静电屏蔽作用导致肌球蛋白纤丝解离,由此也会对肌球蛋白分子结构有一定的保护作用,热稳定性相对较好。

Tilapia was used as material to extract myosin. The effects of heat treatment （40 -80℃ , 1 ℃/min） on the turbidity, solubility, surface hydrophobicity, α-helix content and aggregated particles of myosin were investiga- ted under different ionic strength （ 1,50,150,300,600 mmol/L KC1）. The results showed that the ionic strength and heat treatment significantly affected thermal denaturation and aggregation of myosin. Myosin has poor solubility be- cause of it assembles and forms a filamentous polymer under low ionic strength （ 1 - 150 mmol/L KC1） , after heating treatment, molecular aggregation precipitation, the solubility and or-helix content decreased （p 〈0.05） , the thermal stability of the myosin in this system was undesirable. While under the high ionic strength （300 -600 mmol/L KC1） , myosin dissociated into monomer, the solution is clear. When the temperature is higher than 50℃ , an increase in turbidity and decrease in solubility of tilapia myosin was detected, accompanied by increasing in surface hydrophobici- ty and a significant loss of or-helix （p 〈 0.05） , but the molecular aggregation was not obvious. The results indicated that the electrostatic shielding of high salt ions inhibited formation of myosin filament, which also protected the molec- ular structure of myosin. Therefore, the myosin that under the high ionic strength has the better stability.