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Effects of pH on self-assembly of silver carp myosin at low temperature

Wei, Li, Cao, Liwei, Xiong, Shanbai, You, Juan, Hu, Yang, Liu, Ru
Food bioscience 2019 v.30 pp. 100420
Ca2-transporting ATPase, Hypophthalmichthys molitrix, absorption, confocal laser scanning microscopy, electrostatic interactions, enzyme activity, hydrophobicity, myosin, pH, particle size, protonation, solubility, temperature, turbidity
The effects of pH on myosin self-assembly at low temperature to improve the structural attributes by controlling the solution conditions were studied. Myosin from silver carp was dissolved in solutions at various pH (5.0, 5.5, 6.0, 6.5, 7.0, 8.0 and 9.0). Effects of pH on the particle size, intermolecular forces, and micro-morphology of myosin at low temperature were investigated. The structures of myosin assemblies were observed to be influenced by varying pH using the variations in the degree of protonation and surface charge state of myosin molecules. The low electrostatic repulsion in acidic conditions resulted in the assembly before unfolding of myosin, leading to a relatively high turbidity and UV absorption as well as a decreased solubility. Confocal laser scanning microscopy analysis showed that myosin assemblies with coarse filamentous structure were formed in acid conditions. In alkaline conditions, the increased electrostatic repulsion led to a higher rate of unfolding than assembly and exposure of more hydrophobic residues, as showed by increased S0-ANS values and free SH contents. This relatively high rate of unfolding contributed to the formation of assemblies with a fine and ordered structure. At pH 7.0, the most active structure of myosin molecules was maintained as shown by the highest Ca2+-ATPase activity. Myosin assemblies with an ordered and uniform structure were obtained at pH 7.0.