Photochemical Sciences Ph.D. Dissertations

Probing Lipid Membrane Interactions with Drug Molecules and Cationic Proteins Using Combined Experimental and Computational Analysis

Date of Award

2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Photochemical Sciences

First Advisor

Hong Lu (Committee Chair)

Second Advisor

Dryw Dworsky (Other)

Third Advisor

Joseph Furgal (Committee Member)

Fourth Advisor

John Cable (Committee Member)

Abstract

The lipid bilayer's integrity is essential for cell function as it acts as the primary barrier against external molecules like drugs and peptides, which can alter the bilayer's physical properties. This dissertation investigates how amphetamine (AMPH) and methamphetamine (METH), and the charged HIV1-TAT peptide impact the stability of lipid bilayers, using a home-built lipid bilayer apparatus that enables real-time monitoring through electrical and fluorescence measurements. Our findings indicate that AMPH and METH increase the lipid bilayer's ion permeability, with METH having a greater destabilizing effect. High concentrations of these stimulants, akin to levels in blood plasma of individuals with stimulant-related brain injuries, lead to pore formation in the bilayer. The extent of destabilization correlated with the drug concentration. We also studied the translocation dynamics of the charged HIV1-TAT peptide across the lipid bilayer. The analysis of current fluctuations showed that successful translocation of the TAT peptide is concentration-dependent, highlighting the significance of charge in inducing membrane deformation or pore formation. Additionally, molecular dynamic simulations were used to explore AMPH interactions with the lipid bilayer in greater detail. The results revealed AMPH's preferred orientation during interaction and its hydrophobic nature, as evidenced by the larger energy barrier encountered in the hydrophilic head group regions of the lipid bilayer. To complement these findings, we utilized surface-enhanced Raman spectroscopy (SERS) to estimate the concentrations of AMPH within lipid bilayers. The data showed a positive correlation between characteristic peak heights and AMPH concentrations. Moreover, whole-cell patch clamp measurements on neuronal cells were employed to examine AMPH's effects in a more intricate lipid environment. This research contributes to the understanding of how stimulants and charged peptides interact with lipid bilayers, which is vital for insights into their biological impacts and in developing therapeutic interventions.

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