Unfolding beheavior of Tilapia myosin induced by different acids

Myosin was extracted from Tilapia meat using ammonium sulfate precipitation in this study. Theacid -induced unfolding was carried out at pH2.0 and pH 3.0 by HCl, H2SO4, H3PO4 and C6H8O7, at protein concentration of 2 mg/mL. Solubility, surfacehydrophobicity, total and active sulfhydryl content, intrinsic tryptophanfluorescence spectra and circular dichroism were determined, changes of conformation of tilapia myosin during acidinduced unfolding were studied. Results showed that surface hydrophobicity and reactive SH content of myosin increased by different acid treatments, tryptophan fluorescence intensity and -helix content decreased, suggesting acid-induced unfolding of myosin. And at pH 2.0, myosin had a greater degree of unfolding than that at pH 3.0. Incomparison, the C6H8O7-induced unfolding degree was the highest at pH 2.0 and the -helix content of myosin decreased from 41.7% to 20.5%. However, at pH 3.0, the H2SO4-induced unfolding degree was the highest, and resulted in the significantly decline of solubility. The denaturation of myosin during HCl-induced unfolding was the minimum, and no obvious change of -helix content was obtained, indicating that myosin molecules was stable and retained a molten globulestate