Eugene Florio

Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Glycosphingolipids are the carbohydrate-bearing lipids of animal cells. These usually minor constituents of the plasma membrane have been proposed to have major roles in structure and recognition. Glycosphingolipids are distinctly different from phospholipids in that: (i) they possess donor H-bonding groups, (ii) they often have disproportionately long, single fatty acid chains and (iii) they can be {dollar}\alpha{dollar}-hydroxylated on the fatty acid chain.;As part of a research program to investigate the behaviour and interaction of glycosphingolipids in biological membranes we have developed spin labelled and deuterium labelled derivatives. These included novel 24-carbon (lignoceric acid) spin labelled at C-12 or C-16, and also perdeuterated lignoceric, stearic and {dollar}\alpha{dollar}-hydroxy-stearic acid. Spin labelled fatty acids were linked to simple neutral glycosphingolipids such as galactosyl ceramide and lactosyl ceramide (dihydro) as well as to the complex neutral glycosphingolipid globoside and to the charged ganglioside, G{dollar}\sb{lcub}\rm M1{rcub}{dollar}. Probe-labelled glycosphingolipids were assembled at low concentrations in bilayer model membranes to mimic the situation in cell membranes. EPR and {dollar}\sp2{dollar}H NMR spectra generated with these labelled glycosphingolipids provided data for quantitation of dynamic properties.;For a glycosphingolipid bearing spin-labelled lignoceric acid (24-carbon) (in all of the phospholipid matrices), DMPC (14 carbon), DPPC (16 carbon), DSPC (18 carbon) and DPPC/cholesterol, the order parameter S was always greater than for a glycosphingolipid bearing a stearic acid (18 carbon) acyl chain. We interpreted this as indicating that interdigitation was occurring in the fluid state.;The technology of probe-labelled lipids for assembly into liposomes was extended to Magnetic Resonance Imaging--a recent diagnostic modality employed to visualize body organs and any related pathology, which may accompany it. By employing paramagnetic species such as Gd{dollar}\sp{lcub}3+{rcub}{dollar}, one can alter the relaxation rate of free water, hence augmenting visual definition of organs via contrast enhancement. We have developed liposome-associated contrast agents for in vivo use: a spin labelled phosphatidylcholine and a metal chelator, phosphatidylethanolamine-diethylenetriaminepentaacetic acid. Both of these nontoxic, liposome preparations target the reticuloendothelial system when injected intravenously and were effectively used to highlight liver and spleen of experimental animals.



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