Date of Award

Spring 2015

Project Type

Dissertation

Program or Major

Biochemistry

Degree Name

Doctor of Philosophy

First Advisor

Thomas M Laue

Second Advisor

Rick H Cote

Third Advisor

Feixia Chu

Abstract

Phospholipids (PL) are a major, diverse constituent of cell membranes. PL diversity arises from the nature of the fatty acid chains, as well as the head group structure. The head group charge is thought to contribute to both the strength, and specificity of protein-membrane interactions. Furthermore, the divalent cations Ca2+ and Mg2+, have been shown to be essential for optimal binding for some of these interactions. Because it has been difficult to measure membrane charge, it has been impossible to quantitate the role charge plays in these interactions. However, Nanodiscs provide a stable, planar membrane bilayer suitable for biophysical studies. Here we present the first measurements of the charge on Nanodiscs containing neutral (POPC and POPE) and anionic (POPS, POPA, and PIP2) PLs in varying ratios, and in different solvent conditions. The data reveal that: 1) Nanodiscs provide high-quality charge data using membrane-confined electrophoresis (MCE), and; 2) Nanodiscs exhibit polyelectrolyte behavior. Therefore, the technique of MCE combined with the technology of Nanodiscs give us the ability to develop a simple, reproducible way to analyze lipid charge under physiological conditions; which can clarify inconsistencies between data obtained using various analytical techniques, membrane systems, and experimental conditions.

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