Dynamicqspace microscopy of cellular tissue

Abstract

A multiple exponential time series expansion is used to analyse the dependence of the NMR pulsed gradient spin-echo amplitude S(q, Δ, τ) on the wavevector q, the pulsed gradient separation Δ and the 90–180° pulse separation τ in multicompartment systems such as cellular tissue. The static structure factor measured in q space microscopy is obtained as the lowest order coefficient in the time expansion at long Δ. Dynamic information is obtained from the wavevector dependence of the higher order coefficients. Spatially inhomogeneous relaxation is shown to distort the apparent static and dynamic structure factors. Changes in compartment morphology alter the coupling of relaxation and diffusion reflected in the wavevector dependent relaxation times obtained when Δ and τ are varied together. By fitting the data for parenchyma tissue of apple with a numerical cell model, a plasmalemma membrane permeability of 1·2 × 10^-3 cm s^-1 is derived.