Identification of Restricting Factors That Inhibit Swelling of Oxidized Myofibrils during Brine Irrigation

Porcine longissimus myofibrils were exposed to a hydroxyl radical-oxidizing system (10 mu M FeCl3, 100 mu M ascorbic acid, 1 mM H2O2) at pH 6.2 for 1-12 h. Chemical analyses (sulfhydryls, disulfide bonds, carbonyls) indicated mild protein oxidation along with almost 40% loss of protein extractability in low-ionic-strength brines (<= 0.4 M NaCl, 10 mM pyrophosphate, pH 6.2). Upon graded brine irrigation (0.2-0.6 M NaCl) with pyrophosphate, the swelling of myofibrils and the dissolution of the A-band of oxidized myofibrils were less pronounced than those of nonoxidized. This restriction of myofibril swelling, caused largely by disulfide cross-linkages formed between oxidized myosin tails, was positioned on the transversely expansible thick filaments, reflecting a significant role and susceptibility of intra- as well as intermyofilamental structures.