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, <I>Halobacterium salinarium</I> and <I>Natronobacterium magadii </I>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 <I>H. salinarium</I> 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 <I>H. salinarium</I> studies of permethylated derivatives provided complementary structural information. <I>H. salinarium</I> was shown to contain PGP-ME, S-DGD, PC and PGS with C<SUB>20</SUB>-C<SUB>20</SUB> 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 <I>N. magadii </I>with C<SUB>20</SUB>-C<SUB>20 </SUB>and C<SUB>20</SUB>-C<SUB>25</SUB> 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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:638597 |
| Date | January 1998 |
| Creators | Qui, D. |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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