Characterization of antimicrobial peptide activity by electrochemical impedance spectroscopy

Abstract

Summary Electrochemical impedance spectroscopy performed on surface-supported bilayer membranes allows for the monitoring of changes in membrane properties, such as thickness, ion permeability, and homogeneity, after exposure to antimicrobial peptides (AMPs). We show that two model cationic peptides, very similar in sequence but different in activity, induce dramatically different changes in membrane properties as probed by impedance spectroscopy. Moreover, the impedance results excluded the “barrel-stave” and the “toroidal pore” models of AMP mode of action, and are more consistent with the “carpet” and the “detergent” models. The impedance data provide important new insights about the kinetics and the scale of the peptide action which currently are not addressed by the “carpet” and the “detergent” models. The method presented not only provides additional information about the mode of action of a particular AMP, but offers a means of characterizing AMP activity in reproducible, well-defined quantitative terms.

Atomic Force Microscopy and Electrochemical Studies of Melittin Action on Lipid Bilayers Supported on Gold Electrodes

“…Electrochemical methods were demonstrated to be useful for monitoring the structural changes in supported lipid bilayers occurring upon action of membrane disrupting peptides [20][21][22][23]. We use cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in order to verify the permeability of intact lipid films and then after their exposure to melittin.…”

Antimicrobial peptides: The ancient arm of the human immune system

“…At a critical threshold concentration, the peptides disrupt the membrane finally leading to the formation of micelles or small peptide-lipid aggregates. 8 How AMPs traverse polysaccharide capsules, the outer membrane of Gram-negative bacteria and the peptidoglycan cell wall of both Gram-negative and Gram-positive bacteria before inserting into the cell membrane is largely unknown. Nevertheless, binding of AMPs to anionic lipopolysaccharides and teichoic acids, respectively, is crucial for their activity, since modification of the bacterial envelope leading to charge reduction is a common mechanism of bacterial resistance against cationic AMPs.…”

“…However, considerable sequence similarity was detected between the C-terminal domain of IL-8/CXCL8 and Hp (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), a cationic amphipathic antimicrobial peptide produced by Helicobacter pylori. 158 A corresponding synthetic peptide (amino acid residues 80 to 99 of IL-8/CXCL8) appears to possess significant antimicrobial activity regardless of some conflicting reports possibly reflecting different assay conditions.…”

Membrane Curvature-sensing and Curvature-inducing Activity of Islet Amyloid Polypeptide and Its Implications for Membrane Disruption

“…Other mechanisms have been suggested that are analogous to those utilized by antimicrobial peptides (22)(23)(24). Peptides that employ the detergent-like carpet mechanism cause widespread defects throughout the membrane surface in a nonspecific manner (25)(26)(27)(28). Pore models, in contrast, entail monomers assembling to form a discrete oligomer in the membrane that acts as a pore with ion channellike properties (29,30) or, alternatively, peptides inducing the membrane to form a toroidal pore lined by its own phospholipids (31)(32)(33).…”