ESTIMATION OF WATER-CONTENT AND WATER MOBILITY IN THE NUCLEUS AND CYTOPLASM OF XENOPUS-LAEVIS OOCYTES BY NMR MICROSCOPY

NMR microscopy is a noninvasive approach for studying cell structure a nd properties. Spatially resolved measurements of the relaxation times T-1 and T-2 provided information on the water proton spin density and water mobility in different parts of Xenopus laevis oocytes. The spin -lattice relaxation time T-1 was determined using a saturation-recover y sequence and the common spin-echo sequence with increasing repetitio n times, while the transverse relaxation time T-2 was measured by mean s of the spin-echo sequence with varying echo times. From the relaxati on times, the mole fractions of possible reorientational correlation t imes tau(c) for different types of intracellular water were calculated according to a simple two-phase model. The values for T-1, T-2, and p roton spin density (i.e., water content) are: nucleus >> animal cytopl asm > vegetal cytoplasm. Based on the estimation of tau(c), nearly 90% of the nuclear water and 74.4% of the water of the animal pole was co nsidered as free mobile water, whereas 55.5% of the water of the veget al pole appeared as bound water.