Role of hydration of polyhydroxy compounds in biological systems

The spin-lattice relaxation times, T1, of H2(17)O have been measured for aqueous solutions of 9 polyols as a function of the concentration at 25 degrees C. The dynamic hydration number, nDHN, for polyols were obtained. The values of nDHN increased with an increase in the number of OH groups and depended on the conformation of isomers. The value of nDHN for inositol was the largest. This means that the thermal motion of water molecules around inositol is most inhibited among the polyols studied. The increment of thermal stability of proteins by polyols and sugars, the equilibrium distribution coefficients of polyols and sugars in the denatured hemoglobin solution, and the effect of sugars on the osmotic flow of water were expressed by linear relation of nDHN. On the bases of these relations, a systematic treatment for the effect of hydration of polyols and sugars on these phenomena is discussed.