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Title: Bacterial outer membranes : LPS and the role of lipid rafts in mediating host invasion
Author: Ciesielski, Filip I.
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2013
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Lipopolysaccharide is an essential component of outer membranes in Gram-negative bacteria and there is increasing evidence that it might be involved in mediating host invasion via a direct interaction with host cell membrane. Also, many pathogenic intracellular bacteria, such as Brucella spp., use lipid rafts-dependent entry to mimic endocytic pathway and avoid lysosoma l degradation. In th is project, solid state NMR (ssNMR) spectroscopy and fluorescence spectroscopy are used to investigate possible interactions between bacterial LPS and membranes with raft-like composition. A ssNMR technique for studying changes in lipid dynamics during LPS/ membrane interactions was first developed and J- resolved 13C MAS NMR was used to study changes to DPPC membranes in response to temperature variation and in the absence of isotopic enrichment. J- resolved 20 HETCOR NMR spectroscopy was also developed to investigate more complex lipid membranes and was applied to DOPC/cholesterol and triple mixture DOPC/ SM/Chol, a model membrane used to mimic lipid rafts. Interactions between membrane-incorporated LPS and raft- like membranes were then investigated using 13C MAS NMR as well as 31p NMR spectroscopy. Results revealed that endotoxins undergo significant mobility restrictions in the presence of sphingomyelin and cholesterol suggesting that they partition into the liquid-ordered phase. Fluorescence spectroscopy was then used to study interactions between free LPS and membranes with and without latera l domains showing a preferred affin ity of endotoxins towards bilayers with raft-like composition over plain PC membranes, in agreement with the NMR data. ; ..
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available