The effect Of Dimethylsulphoxide on the phase behaviour of model lipid membranes using small angle scattering

Malik, U 2018, The effect Of Dimethylsulphoxide on the phase behaviour of model lipid membranes using small angle scattering, Masters by Research, Science, RMIT University.


Document type: Thesis
Collection: Theses

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Title The effect Of Dimethylsulphoxide on the phase behaviour of model lipid membranes using small angle scattering
Author(s) Malik, U
Year 2018
Abstract Dimethyl sulfoxide (DMSO) is a universal solvent which has diverse applications in research, medicine and industry. It is a commonly used cryoprotectant in cellular systems, preventing the cellular damage caused by freezing. While the physical and chemical properties of DMSO are understood, its effects on lipid bilayers have only previously been studied under a limited range of conditions, and its mechanism of action in membrane protection remains unresolved. In particular, the location of DMSO within a membrane-water system at modest hydration is unclear. This thesis presents an experimental investigation into the effects of DMSO on the structure of phospholipid membranes as functions of DMSO/lipid ratio, temperature and hydration. Small angle X-ray scattering (SAXS) and Differential Scanning Calorimetry (DSC) are used to determine the phase behavior of this system at a range of hydrations in the temperature range 20°C – 90°C. Experiments are conducted on randomly oriented stacks of model lipid bilayers of DPPC. Membrane structure and phase behavior were studied as a function of the molar ratio of DMSO to lipid, and experiments were conducted using DSC and both laboratory based and synchrotron SAXS.

Data from these complimentary techniques show that DMSO increases the gel-fluid transition temperature, effectively dehydrating the membranes. However, the dehydrating effect becomes less pronounced at lower hydrations, with virtually no effect for samples equilibrated to 57% relative humidity. DMSO also has significant effects on the average spacing between repeating layers, and on the average distance between lipid chains in both the fluid and gel phases. These results provide insight into the interaction between DMSO and lipid bilayers, and allow us to infer the location of DMSO within the lipid/water system. This is the first experimental study to demonstrate that DMSO must reside in the bilayer (rather than transiently passing through), and this insight will inform future research into understanding cryoprotectant action.
Degree Masters by Research
Institution RMIT University
School, Department or Centre Science
Subjects Biological Physics
Thermodynamics and Statistical Physics
Soft Condensed Matter
Keyword(s) DPPC
DMSO
SAXS
DSC
LIPID PHASES
CRYOPROTECTION
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Created: Mon, 14 May 2018, 09:12:53 EST by Denise Paciocco
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