STUDY OF SPIN-LATTICE AND SPIN-SPIN RELAXATION-TIMES OF H-1, H-2, AND O-17 IN MUSCLE WATER

Spin-lattice (T1) and spin-spin (T2) relaxation times of proton, deuteron and 17O in muscle water were measured at 9.21 MHz in the temperature range of 0.degree.-40.degree. C. The values of the apparent activation energy for the 3 nuclei are (in kJ/mol) 9.1, 19 and 18 for 1/T1, and -1.3, 4.2 and 14 for 1/T2, respectively. The relatively small values for T2 for 1H and 2H and their low apparent activation energies are attributed to hydrogen exchange between water and proteins; this exchange does not affect the 17O relaxation. Quantitative calculations on deuteron T1 and oxygen-17 T1 and T2 were made. The effect of surface-induced anisotropy on a minor fraction of water molecules is considered in some detail, and a new expression for its spectral density similar to that of liquid crystalline systems is applied in the calculation. Water on the surfaces of macromolecules may have a rotational correlation time of .tau.c .apprx. 1 .times. 10-9s, with a time constant of .tau.x .apprx. 3 .times. 10-7s, which is characteristic of the relaxation of the local structure.