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Title: Investigation of Archaebacterium lipids by chromatography/mass spectrometry
Author: Qui, D.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 1998
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The Archaebacteria are thought to be a separate domain of ancient micro organisms which have evolved under the harsh conditions of temperature, salinity and absence of oxygen. The membrane of Archaebacteria is made of lipids of unusual structure and many functions are completed by their membrane lipids. In this thesis, studies of the structures of the lipids of two species of Archaebacteria, Halobacterium salinarium and Natronobacterium magadii have been undertaken to provide a better understanding of Archaebacteria. Early chapters introduce the Archaebacterium family, discuss the classification of lipids and the nature of the lipids present in Archaebacteria. This is followed by a discussion of the principles of chromatography and mass spectrometry with emphasis on the techniques used in these studies. Later TLC/scanning densitometry is demonstrated as a viable method for the isolation of the three major lipids of H. salinarium and supercritical fluid extraction (SFE) has been shown to be an alternative extraction method for the isolation of the lipids. The remaining chapters discuss the use of GC/EIMS, GC/CIMS, LC/APCIMS and LC/ESMS for the identification of TLC fractions. The GC/MS techniques used with permethylated, deuteriopermethylated and trimethylsilylated derivatives of the dialkylglycerol ethers obtained from the lipid extracts by removal of the phosphate groups enabled these ethers to be characterised. The LC-MS studies enabled the lipids to be studied and LC-APCIMS proved to be equally effective in both positive and negative ionisation modes, whereas LC-ESMS was most effective in the negative ionisation mode. In the case of H. salinarium studies of permethylated derivatives provided complementary structural information. H. salinarium was shown to contain PGP-ME, S-DGD, PC and PGS with C20-C20 diethers and the presence of up to triunsaturated species was shown. PGP-Me', PGP-Me", PG' and PG" were found as the major compounds in N. magadii with C20-C20 and C20-C25 diethers. Minor lipids, diglucosylglycerol diethers were also found in this extract. Use of direct injection of TLC samples with ES/MS and ES/MS/MS confirmed the structures of the major lipids present.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available