Abstract: 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.

Key words: L-cysteine, atomic?force?microscope (AFM), myosin, morphology