Non-solvent Water in Muscle

Abstract

IT is well established¹ that the structure of water in the vicinity of any surface is different from that of bulk water; also, nuclear magnetic resonance and dielectric relaxation studies have shown that, both in vitro and in vivo, the water adjacent to proteins and other macromolecules is oriented and its motional freedom is impeded^2–6. Furthermore, water exerts a significant stabilizing effect on the structure of some macromolecules^7–9. But there is still considerable debate^10–16 concerning (1) the ability of the water of hydration of intracellular proteins to participate in osmotic changes occurring when cells are placed in hyper or hypotonic solution, and (2) the amount of osmotically inactive water in cells in normal physiological conditions. I wish to report a change in the space accessible to dimethyl sulphoxide in isolated guinea-pig intestinal smooth muscle induced by cooling the muscle from +37° C to −7° C in the absence of ice crystal formation. Dimethyl sulphoxide (DMSO) is a polar, water-miscible non-electrolyte which can form hydrogen bonds only by accepting hydrogen (by contrast, water is an acceptor and donor of hydrogen bonds). The kinetics of permeation of DMSO in smooth muscle have been studied previously¹⁷ and this non-electrolyte has been used with some success in preventing damage to smooth muscle exposed to sub-zero temperatures^18,19.