Proton and deuteron relaxation of muscle water over wide ranges of resonance frequencies.

The spin-lattice relaxation time (T1) of water protons in mouse muscle was studied from 10(4) to 10(8) Hz at several temperatures, and the deuteron T1 of muscle water was studied from 2.0 X 10(3) to 1.54 X 10(7) Hz at several temperatures. Proton T1's of muscle and brain water with different D2O contents were measured at 25 degrees C and 35 MHz. From the results of variable frequency and temperature measurements and the data of isotope substitution, it is concluded that the major relaxation mechanism for the protons in muscle water is the intermolecular dipolar interaction between the protons of the macromolecules and the protons of the water molecules in the hydration layer. It is also suggested that the relaxation of deuterons can be accounted for a very small fraction of water molecules directly hydrogen-bonded to the macromolecules.