Document Type

Thesis

Degree Name

Master of Science (MSc)

Department

Chemistry

Program Name/Specialization

Biological and Chemical Sciences

Faculty/School

Faculty of Science

First Advisor

Dr. Masoud Jelokhani-Niaraki

Advisor Role

Primary Supervisor

Second Advisor

Dr. Matthew Smith

Advisor Role

Co-Supervisor

Third Advisor

Dr. Lillian DeBruin

Abstract

This study aims to expand the understanding of interactions between membrane lipids and proteins, and relate it to their biological functions in two experimental systems. The first system focuses on the interaction and conformation of a membrane protein Uncoupling Protein 4 (UCP4) in mitochondrial inner membrane lipids, in the absence and presence of cardiolipin; a lipid specific to mitochondrial inner membranes. The second system considers the interaction and conformation of a cell penetrating peptide, Penetratin, which can interact with both mammalian and bacterial cells. A N- and C-termini protected form of this 16-meric peptide (Pen2) was used to explore its interaction with neutrally and negatively charged mammalian cell model membranes, as well as negatively charged bacterial cell membrane mimics to study its antibacterial potential. In both systems surface pressure analysis including compression isotherms, adsorption kinetics, and protein-lipid affinities using Langmuir-Blodgett trough tensiometric methods was employed. Circular dichroism (CD) spectroscopy was used to assess the conformation and modes of interaction of the proteins in various lipid systems. Isothermal titration calorimetry (ITC) was used to explore the thermodynamics of binding of Pen2 with lipid membrane models. Comparing these different phospholipid environments mimicking mammalian and bacterial membrane systems allows for an in-depth biophysical understanding of the protein-lipid interactions on the surfaces of cell membranes. Overall, the findings of this study may have broader implications for understanding that the biophysical principles, notably surface pressure, are critical for a wide range of cellular processes. The results of this research on UCP4 and Pen2 provide new insights into the influence of the physiochemical properties of lipids on the conformational/functional properties of MPs and the mechanism of action of MAPs in membranes. In particular, the role of UCP4 in stabilizing the membrane structure at lower surface areas and higher surface pressures and the variability of the modes of interaction of Pen2 with different biological membranes (mammalian vs. bacterial cell membranes).

Convocation Year

2023

Convocation Season

Fall

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