Pore Forming Properties of Alamethicin in Negatively Charged Floating Bilayer Lipid Membranes Supported on Gold Electrodes

Abstract

Electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), and photon polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) were employed to investigate the formation of alamethicin pores in negatively charged bilayers composed of a mixture of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and egg-PG floating at gold (111) electrode surfaces modified by self-assembled monolayers of 1-thio-β-D-glucose (β-Tg). The EIS data showed that the presence of alamethicin decreases the membrane resistivity by about 1 order of magnitude. PM-IRRAS measurements provided information about the tilt angles of peptide helical axis with respect to the bilayer normal. The small tilt angles obtained for the peptide helical axis prove that the alamethicin molecules were inserted into the DMPC/egg-PG membranes. The tilt angles decreased when negative potentials were applied, which correlates with the observed decrease in membrane resistivity, indicating that ion pore formation is assisted by the transmembrane potential. Molecular resolution AFM images provided visual evidence that alamethicin molecules aggregate forming hexagonal porous 2D lattices with periodicities of 2.0 ± 0.2 nm. The pore formation by alamethicin in the negatively charged membrane was compared with the interaction of this peptide with a bilayer formed by zwitterionic lipids. The comparison of these results showed that alamethicin preferentially forms ion translocating pores in negatively charged phospholipid membranes.

Accelerated Molecular Dynamics Applied to the Peptaibol Folding Problem

“…Upon evaluation of Alm orientation based on mathematical models, it was proposed that ion-channels may be formed either by N-terminal integration as monomers or as parallel oligomers. Abbasi et al [25] visualized the formation of Alm pores in floating phospholipid membrane on gold electrodes, which confirmed the hexamer ion channel formation with the diameter of a pore calculated to be 2.3 ± 0.3 nm. A distribution of various Alm aggregates also confirmed the multiple conductivity states theory.…”

Alzheimer's disease-related amyloid β peptide causes structural disordering of lipids and changes the electric properties of a floating bilayer lipid membrane

“…The lowest value of capacitance for the fBLM is equal to 7.3 mF cm À2 , a value typical for fBLMs. 22,32 In the presence of either AbMs or AbOs, the minimum value of capacitance increases to 14.6 or 16.8 mF cm À2 , respectively, thus indicating a decrease in the membrane quality. When the electrode potential becomes more negative, the capacitance of electrodes coated with the three membranes gradually increases.…”

“…These techniques have been successfully applied to study the effect of antimicrobial peptides on the fBLM properties. [19][20][21][22] To demonstrate that the interaction of AbOs with fBLM was unique, we also herein studied the interaction of fBLM with non-toxic AbMs. Apparently, only AbOs could form defects in the membrane.…”

Physicochemical Characterization of Sparsely Tethered Bilayer Lipid Membranes: Structure of Submembrane Water and Nanomechanical Properties

“…It is also more positive with respect to the E pzfc observed for bare gold in 0.1 M NaF demonstrating that the presence of the backfiller inhibits adsorption of anions on electrode surface [19] . Determination of the value of E pzfc is useful for approximate determination of the transmembrane potential, which can be estimated as a difference between potential applied to the electrode ( E ) and the potential of zero free charge ( φ trans = E − E pzfc ) [20] . Knowing the value of the transmembrane potential, it is possible to compare the explored potential range to the values typical for biological membranes.…”

“…[19] Determination of the value of E pzfc is useful for approximate determination of the transmembrane potential, which can be estimated as a difference between potential applied to the electrode (E) and the potential of zero free charge (φ trans = EÀ E pzfc ). [20] Knowing the value of the transmembrane potential, it is possible to compare the explored potential range to the values typical for biological membranes. Further, we have evaluated capacitive behavior of the lipid membranes based on AC voltammograms.…”