Main content

ATOMIC FORCE MICROSCOPY AND ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY STUDIES OF ALAMETHICIN EMBEDDED INTO A BIOMIMETIC MEMBRANE

Show full item record

Title: ATOMIC FORCE MICROSCOPY AND ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY STUDIES OF ALAMETHICIN EMBEDDED INTO A BIOMIMETIC MEMBRANE
Author: Abbasi, Fatemeh
Department: Department of Chemistry
Program: Chemistry
Advisor: Lipkowski, Jacek
Abstract: This thesis is an investigation of the formation of pores by alamethicin molecules in negatively charged bilayers. Unilamellar vesicles of neutral 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and negatively charged 1,2-dimyristoyl-sn-glycero-3-phosphorylglycerol (DMPG) in the absence and presence of alamethicin were fused onto the β-thioglucose modified gold surface. Atomic force microscopy (AFM) and electrochemical impedance spectroscopy (EIS) were employed to investigate the resulting floating bilayer lipid membranes (fBLMs). A direct visualization of the alamethicin pores was obtained from molecular resolution AFM images, revealing that alamethicin forms porous nanoclusters with an average pore diameter of 2.3 ± 0.3 nm. When alamethicin was inserted into the fBLM, a significant decrease in membrane resistivity was observed, indicating that the peptides are forming ion conducting pores. This thesis will also describe the voltage-gated behaviour of alamethicin in a fBLM composed of a mixture of negatively charged egg-PG and neutral DMPC phospholipids. Egg-PG was substituted for DMPG to improve membrane fluidity. At open circuit potential (OCP), the AFM images show that alamethicin molecules inserted into the bilayer form porous nanocluster aggregates within the phospholipid matrix with average pore diameters of 2 ± 0.2 nm. The EIS data collected at OCP show that presence of alamethicin decreases the membrane resistivity by about one order of magnitude. When negative potentials are applied to the electrode, high resolution AFM images show that there is a smooth bilayer on the surface at OCP (0.1 V vs Ag/AgCl), and the bilayer is buckled as the potential stepped to -0.4 V vs Ag/AgCl. The EIS data show that the membrane resistivity changes from 897 ± 85 kΩ cm2 to 153 ± 24 kΩ cm2, when the potential is stepped from 0.1 V to -0.4 V vs Ag/AgCl. The effect of amiloride, an ion channel blocker, on the alamethicin pore formation was investigated. AFM images of DMPC/egg-PG/alamethicin/amiloride show amiloride makes changes on the surface structure of the bilayer and EIS measurements show that amiloride causes a dramatic increase in membrane resistance from 0.89 ± 0.08 MΩ cm2 to 10.6 ± 3.1 MΩ cm2, confirming that amiloride has ion channel inhibiting properties.
URI: http://hdl.handle.net/10214/14431
Date: 2018-11


Files in this item

Files Size Format View
Abbasi_Fatemeh_201811_PhD.pdf 5.302Mb PDF View/Open

This item appears in the following Collection(s)

Show full item record