SULFHYDRYL AND DISULFIDE GROUPS OF PROTEINS : IV. SULFHYDRYL GROUPS OF THE PROTEINS OF MUSCLE.

1. In the denatured proteins of skeletal muscle, the ratio of SH to S-S groups is higher than in the mixed denatured proteins of other tissues, with a single exception-the proteins of the crystalline lens. 2. The number of active SH groups in the proteins of minced muscle or in any of the protein fractions of muscle is only a fraction of the number found after the proteins have been treated with a denaturing agent. 3. The SH groups of the native proteins of muscle are activated by a rise in pH. 4. The relation between pH and number of active SH groups in the proteins of minced muscle and in the various protein fractions of muscle shows that little, if any, denatured protein is present in minced muscle.