Thermophysical characterization of tilapia myosin and its subfragments.

Purified tilapia myosin was digested with α-chymotrypsin and purified to obtain heavy meromyosin (HMM) and light meromyosin (LMM). The thermophysical properties of Tilapia myosin, HMM, and LMM were characterized. Constantly heated myosin, HMM, and LMM samples showed that aggregates began to form around 40 °C as evidenced by the increase of turbidity for all 3 samples (0.25 mg/mL). Beginning turbidity measurements showed differing levels of absorbance for each protein fragment with increasing absorbance values in the following order HMM, myosin, and LMM (0.0026, 0.0282, and 0.052, respectively). Differential scanning calorimetry showed 3 (17.5, 41.9, and 49.9 °C), 2 (43 and 67.1 °C), and 3 (40.4, 51.7, and 69 °C) major peaks for myosin, HMM, and LMM, respectively. Dynamic rheology measurements demonstrated crossover points, which are generally recognized as gelation point, 40.3 °C for myosin and 27 °C for HMM. The results shown for the thermally stable properties of tilapia myosin, HMM, and LMM showed clear evidence that they are all thermal stable at temperatures ranging from 10 °C to approximately 40 °C after which they all are completely denatured. The results also showed that the thermo stability of the myosin and its subfragments were greatly influenced by fish habitat temperature.