Volume-selective and spectroscopically resolved NMR investigation of diffusion and relaxation in fertilised hen eggs

A radiofrequency and field-gradient pulse sequence is presented permitting the non-invasive, volume-selective and spectroscopically resolved determination of incoherent transport parameters with the aid of an NMR field-gradient method. With proton NMR, diffusion or (quasi-incoherent) perfusion coefficients as low as 10(-12) m2 s-1 are accessible with gradients G less than or equal to 100 mT m-1 for T2 greater than or equal to 0.3 s. If coherent motions like flow are superimposed, the gradient pulses can be compensated for phase shifts arising from uniform or accelerated motions. The efficiency of the suppression of the influence of coherent motions was demonstrated in test experiments with phantom sample arrangements. As a biophysical application, the local diffusion coefficients D and relaxation times T1 and T2 of hen eggs were studied during the first days of incubation. In the yolk, strongly non-exponential decay curves were observed for the CH2 line. The translational displacements of water were found to be restricted. The relaxation and diffusion parameters turned out to be constant during the incubation. Medical applications of the pulse sequences are discussed. In one case we demonstrate that attempts to assign resonance lines can be checked by the condition that resonances of the same compound must have identical diffusion coefficients.