1Graduate School of Bioresources, Mie University, Tsu, Mie 514-8507, 2Department of Physics, Suzuka National College of Technology, Suzuka, Mie 510-0294, Japan
The aim of this study was to clarify the effect of gluconate on heat-induced gelation of myosin. Myosin purified from ordinary muscle of red sea bream Pagrus major was incubated at 80°C and then cooled to make heat-induced gel. The breaking strength of the gel formed with gluconate was 4-6-fold larger than that formed with chloride salt. Scanning microscopy showed that the gel with gluconate had a finer and more regular network structure. Gluconate strongly suppressed the thermal denaturation of myosin, but the effect of the suppression was similar to that in the case of sorbitol. On the other hand, gluconate heightened the gel-melting temperature more effectively than sorbitol. The partial specific volume of myosin in sodium gluconate solution was 0.65 cm3/g, which was much smaller than that in sodium chloride solution (0.71 cm3/g). Furthermore, the values of the adiabatic compressibility of myosin in chloride salt solution were positive, while those in gluconate solution were negative, indicating that gluconate remarkably increased the amount of hydration of myosin. These results suggested that gluconate strengthened intermolecular hydrophobic interactions by changing the water structure around myosin molecules.