Dissertation/Thesis Abstract

Determination of Lipid Bilayer Affinities for Small Molecules Using Capillary Electrophoresis and Copolymer-Stabilized Lipid Bilayer Nanodiscs
by Penny, William Michael, Ph.D., University of Montana, 2018, 122; 10932815
Abstract (Summary)

Electrokinetic chromatography is a variation of capillary electrophoresis that allows for the separation of nonionic analytes by selective interaction with an ionic pseudostationary phase dissolved in the background electrolyte. The utility of electrokinetic chromatography to characterize pseudostationary phases and pseudostationary phase–solute interactions has been recognized since its introduction. The objective of this dissertation was to use electrokinetic chromatography and copolymer stabilized lipid bilayer nanodiscs as a pseudostationary phase to characterize small molecule-lipid bilayer interactions.

Styrene-maleic acid copolymers were used to stabilize cylindrical sections of lipid bilayer in solution, forming nanodiscs. The nanodiscs are formed based on strong hydrophobic interactions between the styrene moiety, on the copolymer, and the alkyl tails of the lipids. Using the nanodisc pseudostationary phase, the affinity of the bilayer structure for probe solutes was characterized. Linear solvation energy relationship analysis was employed to characterize the changes in solvent environment of the nanodiscs of varied copolymer to lipid ratio, copolymer chemistry and molecular weight, and lipid composition. Increases in the lipid to copolymer ratio resulted in smaller, more cohesive nanodiscs with greater electrophoretic mobility. Nanodisc structures with copolymers of different chemistry and molecular weight were compared and showed changes in solvent characteristics and selectivity. Seven phospholipid and sphingomyelin nanodiscs of different lipid composition were characterized. Changes in lipid head group structure had a significant effect on bilayer?solute interactions. In most cases, changes in alkyl tail structure had no discernible effect on solvation environment.

The nanodisc pseudostationary phase was also used to study sphingomyelin stereochemistry. Various studies have produced conflicting results regarding whether interactions with lipid bilayers are or can be stereoselective. Using sphingomyelin nanodiscs stereoselective interactions between a pair of atropisomers, R-(+)/(S)-(–) 1,1'-Bi-2-naphthol, were demonstrated.

Finally the dissociation constants between sphingomyelin nanodiscs and solvochromatic analytes were measured and then validated using steady state fluorescence. Using nanodisc affinity capillary electrophoresis, dissociation constants were derived on the same order of magnitude as the dissociation constants derived using the fluorescent technique. Future directions of this project will be to study peptide and protein interactions with lipid bilayers of interest.

Indexing (document details)
Advisor: Palmer, Christopher P., DeGrandpre, Michael D.
Commitee: Berryman, Orion B., Lodmell, Stephen, Ross, Alexander
School: University of Montana
Department: Chemistry
School Location: United States -- Montana
Source: DAI-B 80/01(E), Dissertation Abstracts International
Subjects: Chemistry, Analytical chemistry
Keywords: Affinity capillary electrophoresis, Capillary electrophoresis, Chiral separations, Electrokinetic chromatography, Lipid bilayer, Nanodisc
Publication Number: 10932815
ISBN: 9780438331891
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