¹H-NMR Spectroscopy of the Intracellular Water of Resting and Rigor Frog Skeletal Muscle

Abstract

The intracellular water of intact/relaxed and skinned/rigor fibers of frog skeletal muscle was studied at slack and stretched lengths by use of ¹H-nuclear magnetic resonance (NMR) technique. The angular dependent changes of the NMR spectra of the water proton indicated that part of the intracellular water is aligned along the muscle fiber axis. The longitudinal and transverse proton-spin relaxation processes of the intracellular water were composed of a single- and multi-exponential processes respectively and the rate of both relaxations became slow as the water content of muscle fiber was increased. The longitudinal relaxation process was almost the same at slack and at stretched lengths for both intact/relaxed and skinned/rigor fibers. On the other hand, the transverse relaxation process was slightly but significantly faster at stretched than that at slack length for skinned/rigor fibers while it was almost the same at slack and at stretched lengths for intact/relaxed fibers. These results may be explained as the intracellular water located in the overlap region between actin and myosin filaments is less structured in rigor state than that in relaxed state, or that the rigor formation disrupts the structured water bound to myofilaments.