Light harvesting in low dimensional systems: application of driven Brownian ratchets in supported lipid bilayers for the creation of light harvesting mimics


Supported lipid bilayers are a well known model system for the cell membrane. They allow for the investigation of the membrane in a controlled environment. The solid supported bilayer is accessible through the surface it is formed on and allows for different experimental techniques to be applied. This thesis presents work on free diffusion in the membrane and electrophoretically driven transport concentration of charged membrane components. In addition to that, novel supports for the support of membrane proteins have been investigated and surface enhanced Raman spectroscopy is presented as a label-free method for the detection of membrane components. Brownian ratchets have been used for applications such as molecular sorting with and without the use of lipid bilayers. So far the work has mainly been focussed on their use without a thorough investigation of their properties and the parameters influencing their efficiency. Here, the size and time parameters are varied in experiment and calculation and their role in the ratcheting process is discussed. The efficiency of the ratchets can be significantly reduced when the parameters are chosen in an optimal manner. The use of electrophoresis in lipid bilayers for the concentration and separation of membrane components has focussed on using two electrodes in simple patterns such as squares or lines. This is expanded here on more complex patterns which also allow for the retention of charged material in trapping regions. The pattern was then used to demonstrate the ability to determine binding coefficients in the trapping regions even for membrane components with a low initial concentration or low fluorescence quantum yield. More complex electrode systems using four patterned electrodes are also presented which allow for the application of electric fields in two dimensions where the strength and orientation of the field can be chosen almost arbitrarily. Polymer supports have the ability to support lipid bilayers with membrane proteins which exhibit significant extramembranous domains. Two novel supports are investigated here and different lipid bilayer formation routes are explored. To allow for label free detection of lipids, peptides or proteins within the membrane, surface enhanced Raman spectroscopy is used. The ability of this method to distinguish between different lipids and to detect peptides within the membrane is shown, as well

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This paper was published in White Rose E-theses Online.

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