Pulsed NMR studies on water in striated muscle III. The effects of water content

Abstract

Pulsed NMR is used to study the kinetics of dehydration of frog gastrocnemius muscle. In addition, measurements are reported of the variation of the spin-lattice ( T 1) and transverse ( T 2) nuclear magnetic relaxation times of the water protons as a function of water content. The proton transverse relaxation and freezing properties of the water in muscles which had been dehydrated and then rehydrated are also investigated. Correlation of the double-exponential dehydration kinetics with the transverse relaxation at various water contents provides strong evidence for the evidence of a fraction of muscle water (10–20%) which is sufficiently strongly held to the solid substance of the muscle to make it relatively slowly removed under conditions of zero relative humidity but which is still dynamically very mobile on average. This is supported by the dependence of T 1 on water content. The relaxation times are interpreted qualitatively in terms of a number of possible effects which are at present not distinguishable. The properties of the dehydrated-rehydrated muscles indicated changes in the muscle proteins which affect the transverse relaxation of the water protons and the freezing properties of the muscle water.