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Electrochemical and spectroscopic studies of phospholipid bilayers supported on Au(111) electrodes

Madrid, Elena (2012)
Ph.D. thesis, University of Birmingham.

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Abstract

Electrochemistry and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) measurements were used to characterize the structure and organization of a mimetic biological membrane supported at a Au(111) electrode surface to determine the influence of molecule structure on ensemble properties.

Creation and deposition of mimetic membranes was carried out by combining Langmuir-Blodgett / Langmuir-Schaefer (LBLS) techniques. The LB-LS methodology allows the building of symmetric bilayers and more realistic systems based on a mixture of phospholipids that can be asymmetrically distributed across the bilayer.

The phospholipids that have been studied in this work are DMPC, DMPE and DMPS. They differ from each other in the headgroup. However, they are all symmetric lipids with two saturated acyl chains of 14 carbon atoms.

The electrochemical techniques have characterized the permeability of the film and have detected phase transitions of the lipids at the electrode. PM-IRRAS has provided information regarding the phase state, orientation of phospholipid acyl chains and degree of hydrogen bonding of the headgroup and glycerol region as the applied field was varied.

Results have shown that DMPE bilayers contain less solvent content than DMPC and DMPS bilayers. DMPE molecules packed more tightly due to the hydrogen bonding network between the phosphate and the ammonium group of the neighbouring DMPE molecules which hinder the bilayer from hydration. The hydrocarbon chain orientation was less tilted from the surface normal than that of DMPC but very similar to DMPS at adsorption potentials. During desorption, DMPS has increased hydration of the carbonyl groups and the acyl chains tilted, increasing the compactness between them. The headgroups of DMPS remain hydrated, which increases the capacity of the bilayer.

Type of Work:Ph.D. thesis.
Supervisor(s):Horswell, Sarah L
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Subjects:QD Chemistry
Institution:University of Birmingham
ID Code:3651
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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