Assignment of coherence features in NMR q-space plots to particular diffusion modes in erythrocyte suspensions

NMR q-space plots derived from water diffusing inside and around erythrocyt es in a suspension display reproducible and characteristic coherence featur es. The aim of the present work was to determine which water population giv es rise to the respective features; The central experimental strategy was t o use choline and choline phosphate which are virtually membrane impermeant on the time scale of the experiment; the former was incorporated into eryt hrocytes by a lysis-resealing method and the latter was simply added to the suspensions. Dimethyl sulfoxide, which readily but more slowly exchanges a cross the cell membranes than water, also yielded q-space plots which were similar to those of water, but the differences were able to be accounted fo r on the basis of its slower transmembrane exchange rate. Random walk simul ations using a Monte Carlo procedure, together with a model of an array of biconcave discocytes, helped verify the interpretations of the assignment o f the features of the plots to molecules diffusing in the two regions. In a ddition, the simulations revealed how the presence or absence of transmembr ane exchange affects the form of q-space plots. (C) 1999 Academic Press.