A new method for manipulating charged components of a supported bilayer lipid membrane (sBLM) has been developed. The method makes use of AC electric fields applied in the plane of asymmetrically patterned sBLMs, to rectify diffusion and create net motion in a given direction. This motion has been controlled by tailoring the pattern geometry to perform different functions, and was initially investigated using finite element analysis (FEA), before being shown experimentally. A double-sawtooth pattern was demonstrated to move charges along a narrow channel through the use of an AC field. The operation of this pattern was based on the idea of a Brownian ratchet. Using this pattern, it was shown that a charged fluorescent lipid probe could be transferred in around 25 AC cycles. The double-sawtooth pattern formed the basis of a more advanced "pump" pattern, which was shown to transfer charges from one reservoir into another. This was demonstrated with a fluorescently labelled transmembrane protein. A charge concentrator pattern was also developed. This achieved a 3.5-fold concentration increase in 2 AC cycles. The probe remained in the "trap" region for many hours after removal of the AC field, with a relaxation half-life of around 3.5 h. This pattern was developed further by nesting three traps within one another. The nested trap was demonstrated with a fluorescently labelled transmembrane protein, and yielded a 3D-fold concentration increase after 8 AC cycles. After removal of the AC field, the concentrated protein diffused out from the trap with a half-life of around 2.2 h. Additionally, a computational study of sBLMs with incomplete coverage was done. The study showed that the long-range diffusivity increased linearly with the membrane area fraction, but that the "measured" mobile fraction was unaffected' unless the area fraction was close to the percolation threshold. These results are important for consideration of systems with high protein concentration, or phase-separating mixtures. It is believed that the new method presented here could be used for in- membrane separation and concentration of proteins, and possibly in lab-on- chip devices for bio-analytical techniques.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:559369 |
| Date | January 2011 |
| Creators | Cheetham, Matthew Richard |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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