We studied the order of water molecules in different fragments of nucleus and cortex of
lenses of 3 month old rabbits by investigating the ¹H-NMR spin-spin relaxtion behaviour
of the water protons at room temperature. The experiments were carried out using the
Carr Purcell Meiboom Gill (CPMG) technique. The apparent relaxation rate was found
to be dependent on the pulse spacing in the CPMG sequence in a different way for
nucleus and cortex. While for the nucleus the pulse spacing dependence can be explained
by chemical exchange of water protons, the pulse spacing dependence of the cortex
protons suggests the existence of not fully averaged residual magnetic dipolar couplings
among the protons of a water molecule. To support this interpretation, measurements of
the ratio of the solid echo (90x—90y) to the Hahn echo (90x—180x) amplitude were carried
out for the same samples. These experiments give the expected ratio of =
0.5, characteristic of no residual couplings for the nucleus, but a ratio of =
0.7 for the cortex,
which is characteristic of residual dipolar couplings, caused by anisotropie reorientations
of the water molecules. Thus, evidence for an ordered state of the water molecules in the
cortex has been found
