Agyemang-Yeboah, Francis; (1995) NMR lipid profiling and lipid metabolism in platelets. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Lipid profiles of human blood platelets were obtained employing high-resolution nuclear-magnetic resonance (nmr) in the one-dimensional and two-dimensional modes. The relative amounts of major lipids and their partial assignments were obtained from the spectra of the non-hydrolysed total lipid mixture. The results obtained agreed with similar data obtained by purely chromatographic means, but the nmr method proved more rapid, comprehensive and just as accurate. To extend the information obtained by the nmr approach, the latter was combined with hplc fractionation. The subsequent nmr analysis of the fractionated lipid extracts permitted analysis of the diacylglycerolcholines and ethanolamines, the ether ethanolamines and cholines and the corresponding ceramide (sphingoid) phospholipids. It was also possible to analyse for the C-1 unsaturated and saturated lipids attached to the alkyl-acyl ether lipids. Using the same nmr approach as a novel diagnostic investigative tool, the platelet lipid profile of three cardiac patients were analysed. The results depicted differences in their lipid profiles compared to normal individuals and suggested that this methodology could be used to study lipid metabolic fluxes in pathological conditions involving platelets. The phospholipid transmethylation pathway was also investigated in platelet plasma membranes, purified by a combination of electrophoretic and chromatographic procedures. The major lipid methylating enzyme(s), according to this work, had a molecular weight of 65 ± 2KDa and existed in both acidic and basic forms. These data are consistent with the hypothesis that several SAM-dependent isozymes exist that are responsible for the methylation process. These isozymes may exhibit tissue and substrate specificities.

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