Water structure in striated muscle by spin labelling technique.

The electron paramagnetic resonance (epr) spectra of a nitroxide-type free radical (4-hydroxy-2,2,6,6-tetramethyl-piperidinooxyl, tempol) of equilibrated in muscle water were measured. The results were analyzed in terms of the correlation time or microviscosity. The correlation time of spin probe was only four-five times higher in muscle water than in physiological solutions. The mobility gradually decreased with decreasing relative water content, a restricted mobility having been observed at low relative water content (i equals 0.3) only. The experimental results can be interpreted without assuming the major part of water phase in striated muscle to be ice-like or semicrystalline.