Imaging of voltage-gated alamethicin pores in a reconstituted bilayer lipid membrane via scanning electrochemical microscopy

Abstract

Voltage-gated biological ion channels were simulated by insertion of the peptaibol antibiotic alamethicin into reconstituted phosphatidylcholine bilayer lipid membranes (BLMs). Scanning electrochemical microscopy (SECM) was utilized to probe initial BLM resistivity, the insertion of alamethicin pores, and mass transport across the membrane. Acquired SECM images show the spatial location of inserted pore bundles, the verification of voltage control over the pore conformational state (open/closed), and variations in passive mass transport corresponding to different topographical areas of the BLM. SECM images were also used to evaluate overall BLM integrity prior to insertion as well as transport (flux in open state) and leakage (flux in closed state) currents following insertion.

Glucose and Lactate Biosensors for Scanning Electrochemical Microscopy Imaging of Single Live Cells

“…The Pt 7 μm UME was used for recording topographical images first, with the tip potential E = + 0.6 V vs. Ag/AgCl, 3 M KCl, ensuring the oxidation of the FcTMA. We chose FcTMA as mediator for topography imaging of single cells based on previous work in our lab showing that this particular redox mediator does not cross bilayer lipid membranes (BLMs), 51 i.e., it yields a negative feedback when the UME approaches the BLM. Once the SECM topography information was acquired, the tip potential was switched to E = − 0.5 V vs. Ag/AgCl, 3 M KCl, ensuring the reduction of the oxygen present in the solution, thus yielding oxygen uptake profiles.…”

Electric‐Field Distribution at the End of a Charged Capillary—A Coupling Imaging Study

“…The model fits very well with experimental data. Based on recent developments of SECM imaging on voltage-gated pores in bilayer-lipid membranes [17] and the combined SECM-AFM technique, [18,19] we believe that the coupling-imaging mode is promising to detect and image the electric field near…”

A gramicidin analogue that exhibits redox potential-dependent cation influx

“…Cliffel and co-workers 25 report the observation of the voltage dependent opening and closing of alamethicin pore bundles in phosphatidylcholine BLMs using the redox active Ru(III) hexamine cation as transporting cation using an SECM UME with RG (ratio of the insulator radius to the disk electrode radius) values of 1.4(±0.1). In the case of a small peptidic channel such as gA, which has a pore radius of ~0.2 nm in the β 6,3 conformation, we do not expect to observe single channels; however the behaviour of channel porated membranes resulting from ion permeation through clusters of channels which form a locus for ion accummulation, may be observable.…”