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Title: Tethered biomimetic phospholipid vesicles : a novel method to study membrane permeation
Author: Williams, Thomas Lloyd
ISNI:       0000 0001 3569 5496
Awarding Body: University of Bath
Current Institution: University of Bath
Date of Award: 2007
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The cell membrane provides a barrier and maintains the equilibrium between the intracellular and extracellular spaces. It regulate the flux of ions, metabolites and cellular components, and also acts to regulate the communication between the cells. However, any change in the cell membrane, as a result of mechanical, biological or chemical damage, may significantly alter the structure and function of the cell. Various protein toxins, such as lipolytic enzymes and pore-forming bacterial toxins, have developed means to circumvent this barrier to gain access to resources. The interaction between the toxins and the cell membrane is of interest to understand the mechanisms . involved in a range of toxin-related disorders such as cholera, prion diseases, and snake envenomation. Surface Plasmon Resonance (SPR) provides a technique to simultaneously measure the change in mass density at a surface as a consequence of the adsorption and/or desorption events with a means of exciting fluorescent dye molecules at the surface. The combination of SPR and Surface Plasmon field enhanced Fluorescence Spectroscopy (SPFS) provides a surface sensitive technique with an ability to quantitatively and qualitatively determine small changes in mass and fluorescence in real-time and without the need for labelled molecules, as a result of the toxin-membrane interactions. Biomimetic membrane phospholipid vesicles were constructed as a model cell membranes and provides a means of monitoring the initial interaction events and the subsequent actions the toxins trigger in relation to the membranes. The biomimetic membranes provide a simple and reliable model to study these events. Direct membrane lysis, caused by lipolytic enzymes such as phospholipase A2 (PLA2) can be observed, and the affinity between the enzyme and the membrane determined. The binding between cholera enterotoxin and the biomimetic membrane can be monitored, and changes in the membrane permeability determined. One of the pathogenic hallmarks of Alzheimer's disease is the accumulation of insoluble p-amyloid deposits on the surface of neurons. The biomimetic membrane system provides a means to monitor the initial stages involved in amyloid aggregation and the subsequent toxic events. Understanding th~ mec1wnisms involved between the analyte-ligand interactions provides insight into possible therapeutic targets against these events. Direct membrane lysis due to PLA2 activity was shown to be inhibited by manoalide and eicosadienoic acid, whereas cholera toxin and p-amyloid binding were inhibited by lanthanide trivalent compounds. Therefore, the biomimetic membrane system provides a novel method to study toxin antagonists.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available