Bonzom, Pascale Marie Andree; (1998) High resolution nmr applied to lipid analysis and lipid based drug design. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The following topics were studied, principally by NMR spectroscopy but also, where relevant, by circular dichroism, molecular modelling or chromatography: (1) NMR lipid and metabolite analysis, (2) conformational analysis of polyunsaturated lipids and (3) the design, synthesis and structural studies of conformationally-restrained polyunsaturated fatty acids (PUFAs) analogues. One- and two-dimensional proton NMR techniques were used to characterise and quantify lipids and water soluble metabolites extracted from Agaricus bisporus. Phospholipid classes, sterols and glycerides were determined from structure specific proton-resonances and confirmed by cross peaks in the 2D COSY spectra of lipid extracts. Additional information was obtained by separating the total lipid extract by chromatography and analysing the NMR spectra of the resulting four classes of lipids. I'he main water soluble metabolites involved in the cellular and metabolic pathways were also identified, using combined ID, 2D COSY and 2D-J resolved NMR. Information obtained from NMR experiments proved to be in agreement with previous published data, which was obtained using well established but time-consuming conventional chromatographic techniques. The NMR lipid profiles of blood platelet lipid extracts from healthy individual and patients suffering from coronary artery diseases were compared. Certain features, in particular the phosphatidylcholine to phosphatidylethanolamine ratio, appeared to be dependant on the disease states. In an attempt to develop drugs based on lipid structure, arachidonic acid and higher PUFAs were subjected to molecular modelling. The stable conformations highlighted were used to design a series of lipid mimetics, including peptido-PUFAs where the C=C bonds were replaced by isosteric amide bonds. Since molecular dynamics experiments revealed that the structures had been constrained, these lipids were synthesised and their structure confirmed by circular dichroism and one- and two- dimensional high resolution NMR. High-field NMR has proved to be a versatile technique that has enabled the rapid and comprehensive analysis of biological lipids and metabolites, and also the experimental validation of computational studies leading to drug design.

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