原子力显微镜研究L-半胱氨酸对鲢肌球蛋白溶液热聚集行为的影响

利用原子力显微镜技术分析L-半胱氨酸（L-cysteine，L-Cys）对鲢肌球蛋白热聚集行为的影响。在肌球蛋白溶液中添加5?mmol/L（pH?7.0）的L-Cys溶液，分别进行未加热（25?℃、30?min）、一段式加热（90?℃、30?min）、二段式加热（40?℃、60?min＋90?℃、30?min）处理，分别测定溶解度、表面疏水性、聚集行为表面形貌的变化。结果表明：3?种加热方式低盐条件下L-Cys均显著提高肌球蛋白的溶解度（P＜0.05）；一段式加热时L-Cys显著提高高/低盐条件下肌球蛋白的表面疏水性（P＜0.05），二段式加热时高盐条件下表面疏水性显著提高（P＜0.05），其他条件下表面疏水性无明显变化。高/低盐条件下添加L-Cys均能显著改变肌球蛋白聚集行为的表面形貌，使聚集体更加分散，抑制了肌球蛋白的聚集。L-Cys对肌球蛋白溶解度、表面疏水性的影响进一步影响了其聚集行为，改变其聚集形貌。

Influence of L-Cysteine on the Heat-Induced Aggregation of Bighead Carp Myosin Studied by Atom Force Microscope

The effect of L-cysteine on the heat-induced aggregation behavior of bighead carp myosin was studied using atomic force microscope (AFM). Changes in the solubility, surface?hydrophobicity and aggregate surface morphology of myosin samples with 5 mmol/L (pH 7.0) L-Cys added were measured after being treated at 25 ℃ for 30 min (control), at 90 ℃ for 30 min (one-step heating) or at 40 ℃ for 60 min and then at 90 ℃ for another 30 min (two-step heating). The results showed that L-Cys significantly increased the solubility of myosin in low ionic strength solutions under all three heating modes (P < 0.05). Under both high and low ionic strength conditions, the surface hydrophobicity increased significantly in the presence of L-Cys after one-step heating (P < 0.05), whereas for two-step heating, it increased significantly only under high ionic strength conditions (P < 0.05). Under both high and low ionic strength conditions, added L-Cys remarkably altered the surface morphology of myosin aggregates, loosening the aggregates and inhibiting aggregation. Conclusively, L-Cys affects the solubility and surface hydrophobicity of fish myosin, thereby affecting the aggregation behavior and altering the aggregate morphology.