To elucidate the roles of the head and tail portions of chicken breast muscle myosin in gelation, the thermal stability and aggregation behavior of myosin and seven subfragments in 0.6 M NaCl, pH 6.5, were investigated, namely, myosin heavy chain (MHC), light chains (LC), heavy meromyosin (HMM), light meromyosin (LMM), rod, subfragment 2 (S-2), and subfragment 1 (S-1). Myosin had four independent cooperative endothermic transitions (T_m) at 47, 54, 57, and 63 °C and aggregated from 50 to 70 °C. The MHC endotherm had peaks at 46, 54, and 64 °C and aggregated between 45 and 63 °C. S-1 unfolded in a single transition, having a T_m of 47.7 °C, and aggregated from 49 to 53 °C. The rod melted between 30 and 63.3 °C and continuously aggregated over this temperature range. Initial unfolding of the rod occurred in the LMM region. S-2 was primarily responsible for denaturation and aggregation above 55 °C. Transition temperatures of 48 and 57 °C were recorded for LC; however, no aggregation occurred. The rod had the biggest influence on gel formation. Light meromyosin and S-1 contributed to gel structure at temperatures less than about 55 °C, whereas S-2 was responsible for matrix formation above 60 °C.

Keywords: Myosin; gelation; differential scanning calorimetry; denaturation