Determination of the self-diffusion coefficient of intracellular water using PGSE NMR with variable gradient pulse length

Abstract

A new pulsed-gradient spin-echo NMR protocol for assessing the local self-diffusion coefficient D 0 of water confined within living cells is proposed. Equations for the apparent mean-square displacement < Z 2> as a function of the effective diffusion time t d and the duration of the displacement-encoding gradient pulses δ are derived. The standard method of estimating D 0 – reducing t d until the influence of collisions between the water molecules and the plasma membrane can be neglected – often fails because of the small size of typical cells. As demonstrated here, the decrease of the apparent < Z 2> with increasing δ at constant t d can be utilized to measure D 0.