Suppression mechanism of l-arginine in the heat-induced aggregation of bighead carp (Aristichthys nobilis) myosin: The significance of ionic linkage effects and hydrogen bond effects

The suppression mechanism of l-arginine (Arg) in fish myosin heat-induced aggregation was investigated in this work. The hydrodynamic radius determined by dynamic light scattering (DLS) and the turbidity of a myosin solution decreased in a dose-dependently manner with Arg after heating, especially in a solution without pH modification (P < 0.05). The surface hydrophobicity of myosin exhibited the same trend as that for hydrodynamic radius and turbidity (P < 0.05). The myosin secondary structures clearly changed with Arg concentration during heating (P < 0.05). These results demonstrate that positively-charged Arg could form ionic interactions with negatively charged myosin, as well as promote repulsion between myosin molecules induced by higher pH values. Furthermore, the resultant hydrogen bonding observed indicated that, in addition to Arg having ionic linkage effects, the specific structure of Arg played an important role in the suppression of myosin aggregation. Essentially, Arg markedly disturbed the hydrogen bonds of the myosin backbone and formed new hydrogen bonds with myosin molecules via two amino groups (-NH2), which are part of the guanidinium moiety of Arg, preferentially hydrogen bonding with the backbone carbonyl oxygen atoms of myosin molecules. This work provides support for using Arg as an additive to modify the texture of fish products to produce liquid and semiliquid food suitable for the elderly consumers in an aging society.