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Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 161-172).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 118-126).

A deuteron magnetic resonance study of water has been carried out in the lamellar phase of the egg yolk lecithin-water and outer membrane of E. Coli-water systems in excess water (abbreviated to EYL/EXCD₂O and EC/EXCD₂0, respectively) and egg yolk lecithin-water in 22% (by weight) water (EYL/22%WD₂0). Spectra of these systems were taken as a function of temperature, and their moments were calculated. Analysis of the integrated signal intensities revealed that the excess free (bulk) water in the EC/EXCD₂0 and EYL/EXCD₂O froze at -1°C and -2°C, respectively (pure D₂0 freezes at 4°C). The water from bilayers in the two excess water systems was frozen immediately after it was squeezed out, whereas the water squeezed out from bilayers in the EYL/22%WD₂0 remained unfrozen down to -10°C. All the squeezed out water in the EYL/22%WD₂0was frozen at -15°C. The bound water in that system was unfreezable in the region under study. The amount of water frozen out in the EYL/EXCD₂O at -2°C and in the EYL/EXCD₂O at -3°C was found to be approximately 85% of the total water content of the systems. The water frozen out in the EYL/22%WD₂0 at -15°C was determined to be 50% of the total water in that-;system. A minimum in the second moment vs temperature of the EYL/22%WD₂0 was observed and ascribed to the presence of isotropic free water squeezed out from the bilayers. Proton magnetic resonance results showed that there was no lipid phase transition in the EYL/22%WD₂0 in the region from -10°C to 48°C. / Science, Faculty of / Physics and Astronomy, Department of / Unknown

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If the function of membrane lipids were only to provide a permeability barrier for cells, than a single lipid species such as phosphatidylcholine would suffice since it would maintain the bilayer structure necessary for a membrane. Cells, however, go out of their way to regulate the components of their membranes and therefore there must be some reason for the vast diversity of lipids found even in a single membrane. Modulation of the phospholipid composition could affect both the average and dynamical properties of the entire system. Average properties such as the hydrocarbon thickness, the area per lipid molecule, or the curvature stress across the bilayer could play a role in membrane function and therefore it is important to understand how different lipid components influence these physical properties. The goal of this work has been to understand how different lipid components such as changes in headgroup and acyl chain unsaturation as well as cholesterol and bile salts affect the properties and structure of membranes through the use of deuterium nuclear magnetic resonance spectroscopy (²H NMR). Saturated and unsaturated phosphatidylethanolamines and phosphatidylcholines have been studied in the low temperature, lamellar liquid-crystalline, and reversed hexagonal phases. Measurements have been made of the average projected acyl chain length, the average area per molecule, the radius of curvature in hexagonal phases, and various relaxation rates. These studies were not only carried out on single component synthetic systems but also mixture of lipids and even native membranes through the use of a deuterated probe molecule. It was concluded that different lipids modulate different properties of membranes. Phosphatidylcholines along with monounsaturation keep the membranes in a fluid state whereas the presence of phosphatidylethanolamines and polyunsaturation increase the curvature stress in the monolayers. With this in mind experiments were carried out to determine how the average properties of membranes relate to membrane protein function. These studies show the promise of combining physical chemical measurements of membrane properties with biochemical measures of protein function. Such studies will allow for a better understanding of membrane function and the role lipid diversity plays in such functions.

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Thesis (Ph. D.)--Georgia State University, 2007. / Title from file title page. Phang C. Tai, committee chair; John Houghton Parjit Kaur, Chung-Dar Lu, committee members. Electronic text (148 p. : ill. (some col.)) : digital, PDF file. Description based on contents viewed Dec. 7, 2007. Includes bibliographical references (p. 125-140).

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