No description available.

The use of short high voltage pulses to overcome the barrier of the cell membrane by creating pores is known as electroporation. Pulsed electric fields can cause irreversible and reversible breakdown of the cell membrane thereby this technology can be applicable for sterilization processes as well as to enhance the transportation rate of foreign particles across the membrane. Transformation efficiency still remains the challenging aspect of the process. Due to the limitations of the pulse generators; available, the past research on electroporation has been limited to small treatment volumes with limited flexibility to optimise the process parameters.

The aim of my thesis is to evaluate the use of applied dissolved noble gas tracers for the estimation of flow and transport parameters in permeable reactive barriers (PRBs) and for the assessment of changes in those parameters over time. PRBs consist of reactive materials that are p l aced in the subsurface to intercept a contaminant plume. PRBs have been proven to effectively remediate a variety of groundwater contaminants. The main limitation to the use PRBs as a remediation tool is the build up of mineral precipitates and gases that may inhibit water flow through the barrier, decrease the reactivity of the PRB medium, and reduce the residence time of contaminated water. Applied chemical tracers provide the most direct measurement of how water moves through PRBs to assess the effects of mineral precipitation and gas evolution on flow and transport parameters in PRBs. Tracer experiments in laboratory columns and full scale permeable reactive barriers are described in detail , highlighting advantages and disadvantages of using noble gases as applied tracers. The volatility of noble gases presents advantages and disadvantages. The retardation of dissolved gas tracers, as a result of interactions with gas bubbles trapped in pore spaces, provides information about the volume of a gas phase that is present in the system. However, the degassing of dissolved gas tracers during tracer injection, sampling , and sample preparation can result in many uncertainties with respect initial tracer concentrations. These uncertainties are best dealt with by using multiple noble gas tracers along with a "conservative" tracer such as Bromide or Chloride. This thesis demonstrates that noble gases can be used effectively as applied tracers to assess the long - term effectiveness of PRBs.

No description available.

The presence of membrane microdomains or rafts within cell membranes is an area of intensive research and debate, with the notion of intracellular membrane rafts proving particularly contentious. The full extent of their biological importance is unknown but, they do appear to have vital roles in key processes such as membrane transport and cell signalling. They have been shown to have significant involvement in the formation of the immunological synapse and subsequent immune cell activation. Their cellular functions are also hijacked by various pathogens such as the human immunodeficiency virus and prion diseases, establishing them as important pharmaceutical targets.

To investigate, the interaction of fibronectin with lipids, simplified models of the cell membrane that take into account elements of its' lipid raft structure were examined. Atomic force microscopy (AFM) was employed to characterize the biomolecule adsorption. For binary lipid mixtures that display phase separation, AFM revealed that fibronectin preferentially and almost exclusively interacts with the gel phase domains. Single molecule force spectroscopy confirmed the location of the protein with respect to the lipid topography and allowed mechanical, thermodynamic and kinetic parameters concerning protein unfolding to be determined. Force distance curves also allowed characteristic features of the lipid-protein interaction to be measured in addition to the thickness of fibronectin layers on top of the gel phase domains. The effect of the adsorption of the fibronectin molecules at a lower concentration and at a temperature close to the glass transition temperature of the lipids was also investigated. Gel phase domains were found to self assemble into ring like structures in the presence of low concentrations of fibronectin. Force spectroscopy located the protein on the rings and together with topographic analysis allowed a model for the self assembly process to be proposed. The discovery of these unusual rings suggests that fibronectin has the ability to trigger lipid organisation. Finally α5β1 integrins were reconstituted into supported lipid bilayers in order to create a more biologically relevant model membrane. Topographic analysis demonstrated that the integrins had reconstituted into the bilayer with their head regions protruding from the bilayer as would be expected in a real cell membrane. Moreover the integrin head regions were shown to be functional by subsequent binding of fibronectin molecules specifically onto these head regions. All of these observations with respect to the adsorption behaviour of fibronectin molecules onto lipid bilayers have implications for understanding cell behaviour as fibronectin is more selective and has more of an effect on lipid organisation than previously thought.

The membrane is a key component of cells as it acts as a barrier with the extracellular matrix, preventing alien entities trom entering the cell unnindered. It also provides the medium for membrane embedded proteins to bind and react to small molecule messengers and with other cells. The research described in this thesis is focused on the study of the thiol-disulfide reaction at the membrane interfaces in order to understand how this environment affects reactivity and mechanism relative to aqueous solution. This knowledge informs the design of artificial biomimetic systems based on vesicles, which have long been used as the cell membrane model of choice.

No description available.

No description available.

No description available.