Effects of urea on thermal gelation process of myosin B prepared from shark muscle

The effects of urea concentration on the gel forming ability of shark muscl e were investigated at two characteristic temperatures: aggregation was mea sured at 40 degrees C; and gelation was measured at 70 degrees C. When heat ed to 40 degrees C, the gel rigidity of myosin B decreased when the urea co ncentration was less than or equal to 1.0 M, but it increased when the urea concentration was between 1.0 and 2.0 M. The increase of gel rigidity can be attributed to the formation of an apparent network structure resulting f rom increasing disulfide bond levels. When heated to 70 degrees C, the rigi dity decreased as the uniform network structure broke down with the increas e of urea concentration. The microscopic observation and water distribution analysis revealed that the combined denaturing action of urea and heating resulted in a porous gel with a compact configuration and condensed myosin B network structure.