Tracing Molecular Propagation in Dextran Solutions by Pulsed Field Gradient NMR

We have exploited the pulsed field gradient (PFG) technique of NMR to measure molecular diffusion in aqueous solutions of a mixture of dextran molecules. From detailed studies by fluorescence correlation spectroscopy (FCS), the lighter component of such mixtures is known to undergo subdiffusion, up to diffusion path lengths on the order of 0.5 μm. Our studies provide clear evidence of a crossover to normal diffusion for diffusion path lengths from this range up to about 1 μm.