Simultaneous measurement of vesicle diffusion coefficients and trapping efficiencies by means of diffusion ordered 2D NMR spectroscopy.

It is demonstrated that the fraction of sucrose entrapped in the aqueous compartment of phospholipid vesicles and the tracer diffusion coefficient of the vesicles can be determined simultaneously with diffusion ordered 2D NMR spectroscopy (DOSY). The sizes of the vesicles are related to the diffusion coefficients by the Stokes-Einstein equation. This method displays 1H-NMR peaks for sucrose in the diffusion dimension at positions corresponding to free and entrapped sucrose, and the areas of these peaks are proportional to the amount of free and entrapped sucrose, respectively. The results were verified by a 1D NMR experiment in which the sucrose peaks were integrated before and after dialysis to remove the external sucrose.