Application of transport resolved two-dimensional nuclear magnetic resonance to the study of phospholipid vesicles

Chapter I introduces new two dimensional Nuclear Magnetic Resonance (NMR) techniques, Diffusion and Mobility Ordered Spectroscopy (DOSY and MOSY), and discusses their application to model membrane systems. Also, the theory of translational diffusion and electrophoretic mobility are reviewed.;Chapter II details the experimental aspects. The background and preparation of phospholipid vesicles ranging in size from 250 to 3,000 angstroms are presented. Also, the theory and implementation of Longitudinal Encode-Decode (LED) Pulsed Field Gradient (PFG) and Electrophoretic NMR are discussed. Briefly, the techniques of Dynamic Light Scattering (DLS) and Electron Microscopy (EM) are reviewed.;Chapter III presents the results from LED PFG-NMR for phosphatidylcholine (PC) vesicles. The NMR signal from saccharides entrapped inside the aqueous compartments of vesicles are shown to give lower average diffusion coefficients compared to the phospholipid headgroup resonance for large vesicles. From EM, it is evident that these vesicle samples are polydisperse. The distribution of diffusion coefficients for polydisperse vesicle systems are obtained from DOSY analysis of LED PFG-NMR data. It is shown that as the average vesicle size decreases, the amount of overlap of the diffusion distributions obtained from the entrapped saccharide and headgroup resonances increases. The difference is due to size dependent spin-spin relaxation weighting of headgroup proton resonances.;Chapter IV shows the size distributions obtained from DOSY of PC vesicles of various sizes. The size distributions obtained from the techniques of DLS and EM are shown for comparison. The differences in the data from all three methods are due to differences in signal weighting factors.;Chapter V discusses the results from Electrophoretic NMR for charged vesicle systems. LED PFG-NMR and EM are used to select a suitable charged vesicle system in a low ionic strength solution. MOSY analysis indicates the electrophoretic mobility distribution is sensitive to the amount of polydispersity present. Comparisons of the data to electrokinetic theory are made. Also, this technique is shown to be useful in disclosing sample impurities. Finally, future work is described that will establish experimentally the dependence of electrophoretic mobility on size in a range where the theoretical result has not been firmly established.