The phase properties of lipids have very important consequences for membrane biology. Their influence ranges from the crystallization of membrane proteins, to drug delivery and domain formation in native membranes. To better understand the role that lipids play in these circumstances, it is necessary to study their physical properties. Therefore, the rules relating lipid phase behavior to their molecular structure need to be established.
In this dissertation an effort is made to establish the relationship between the molecular structure of monoacylglycerols and their phase behavior. The major objective is to be able to rationally design lipids with required phase characteristics. The monoacylgylcerol/water phase systems were chosen for study. Using a database of homologous cis-monounsaturated monoacylglycerols with known phase characteristics, the temperature-composition phase diagrams of five monoacylglycerols were predicted.
The phase diagrams of these monoacylglycerol/water systems were worked out. X-ray diffraction was used as a primary tool. In general, data was collected in a 0 to 65 %(w/w) water range, and from -15 °C to 110 °C. When creating a heating direction phase diagram, care was taken to set all samples into the solid Lc phase. Cooling direction phase diagrams were also worked out for these monoacylglycerols. Samples at room temperature were cooled down to -15 or -20 °C.
The predicted and experimental phase diagrams were compared to evaluate the efficacy of the predictions. The predictions were seen to agree with the experimental data, within error. It was seen that better predictions were obtained when a larger number of homologous monoacylglycerols were considered when making the prediction. The relationship between lipid molecular structure and phase behavior was thus established.
Each monoacylglycerol studied was evaluated as a matrix from which membrane protein crystallization of at least one test membrane protein was attempted. Out of the five monoaclyglycerol/water systems described here, four were used successfully to grow membrane proteins. Attempts were made to crystallize other membrane proteins in these monoacylglycerol systems. Crystals of the membrane protein, BtuB, were successfully grown in one of the monoacylglycerols whose phase behavior was determined as part of this project, diffraction data-sets were collected on these crystals.
|School:||The Ohio State University|
|School Location:||United States -- Ohio|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Keywords:||Ca???????rey, Ia3d, L????, Mags, Phase, Phase diagrams|
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