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Microcavity array supported lipid bilayers biomimetic platform for study of membrane associating proteins and membrane-protein aggregation

Robinson, Jack orcid logoORCID: 0000-0002-0447-0822 (2022) Microcavity array supported lipid bilayers biomimetic platform for study of membrane associating proteins and membrane-protein aggregation. PhD thesis, Dublin City University.

Abstract
The plasma membrane is a semi-permeable barrier system. It separates the extracellular and intracellular environments, supports cell-signalling, cell adhesion and membrane transport. Proteins can be embedded in or bound peripherally to the membrane. The living cell membrane’s profound complexity has proven a difficult environment for investigating protein binding mechanisms. This has led to the development of biomimetic model membranes to allow for the study of dynamics and functions of individual cell membrane processes isolated from its complex nature. Chapter 1 describes the background to this work and overviews the current state of the art model membranes. Chapter 2 describes the experimental studies for MSLB preparation and analysis. Annexins are soluble membrane-binding proteins that associate in a calcium dependent manner with anionic phospholipids. They play roles in membrane organization, signalling and vesicle transport and in disease states including thrombosis and inflammation. Annexin V is believed to be involved in membrane repair. Through binding to phosphatidylserine exposed at damaged plasma membrane the protein forms crystalline networks that stabilises small membrane tears. Chapter 3 models this mechanism to simulate membrane healing at microcavity array supported, asymmetric, lipid bilayers. Fluorescence spectroscopy confirmed that when DOPS was made available at the external leaflet annexin assembled rapidly at the membrane where it formed a layer. From electrochemical impedance, the formed layer decreased membrane capacitance whilst reducing resistance. Amyloid peptide aggregation, particularly Aβ (1-42), triggers neurotoxicity and is believed to play a central role in progression of Alzheimer’s disease. An exact link between Alzheimer’s disease and Aβ has not been determined but hypothesized that its self-aggregation of monomeric forms of Aβ to oligomers or fibrils has an important role in the progression of the disease. Chapter 4 investigates the effects of DOPS on Aβ oligomer formation by varying the DOPS & Aβ concentrations, and membrane orientation. It was seen that when more DOPS is present at the external leaflet, less concentration of Aβ is needed to form oligomers before the bilayer is destroyed. Integrins are transmembrane, conformationally switching receptors involved in cell-cell and cell extracellular matrix adhesion. Integrins are believed to exist in conformational states that regulate their affinity to their ligands, proteins, or the extracellular matrix. Normally present in their bent resting state or can be activated to an extended state. Galectins are known to cluster with Integrin. Chapter 5 investigates Galectin-3 clustering on the different states, resting vs activated, of Integrin, α5β1. It was seen that in the resting form, galectin 3 was seen to form oligomers. However, on activation the oligomers of galectin 3 were not observed.
Metadata
Item Type:Thesis (PhD)
Date of Award:November 2022
Refereed:No
Supervisor(s):Keyes, Tia
Uncontrolled Keywords:Biophysics; Fluorescence
Subjects:Biological Sciences > Biosensors
Physical Sciences > Analytical chemistry
Physical Sciences > Chemistry
Physical Sciences > Electrochemistry
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Chemical Sciences
Research Initiatives and Centres > National Centre for Sensor Research (NCSR)
Research Initiatives and Centres > National Biophotonics and Imaging Platform Ireland (NBIPI)
Funders:Science Foundation Ireland, Irish Research Council
ID Code:27309
Deposited On:17 Nov 2022 12:12 by Tia Keyes . Last Modified 17 Nov 2022 12:12
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Creative Commons: Attribution-Noncommercial-No Derivative Works 4.0
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