Modulation of Activity of Ultrashort Lipopeptides toward Negatively Charged Model Lipid Films

Abstract

Because of the increasing resistance of pathogens to commonly used antibiotics, there is an urgent need to find alternative antimicrobial compounds with different mechanisms of action. Among them, lipopeptides are recognized as promising candidates. In this work, the Langmuir technique and atomic force microscopy were employed to investigate the interactions of two novel lipopeptides with negatively charged phospholipid membranes, which served as a simplified model of inner membrane of Gram-negative bacteria. Lipid films contained phosphatidylethanolamine and phosphatidylglycerol extracts from E. coli bacteria. Lipopeptides were composed of palmitoyl chain covalently coupled to N-terminus of peptide with Trp-Lys-Leu-Lys amino acid sequence and the conformation of third residue was either d-Leu or l-Leu. It was found that chirality of leucine strongly affects interfacial behavior of these compounds, which was ascribed to the difference in effective size of the peptide portion of the molecules. Although the lipopeptides were the same in terms of amino acid sequence, charge, and identity of lipophilic chain, the experiments revealed that the barrier for their insertion into the lipid membrane is significantly different. Namely, it was lower for lipopeptide containing d-Leu residue. We have also found that insertion of the lipopeptides into the model membranes strongly alters lateral distribution of the membrane components and leads to its substantial fluidization. The dynamics of reorganization was noticeably faster in the presence of lipopeptide with smaller size of peptide moiety, i.e., containing d-Leu. It proves that effective size of the peptide headgroup is an important factor determining lipopeptide activity toward the lipid membranes.

Physicochemical and Biological Characterization of Novel Membrane-Active Cationic Lipopeptides with Antimicrobial Properties

“…After the injection of the given lipopeptide, the topography of the samples is substantially changed. In all cases, the size of the L β domains is reduced and at the same time, the area occupied by L β is expanded, which is indicative of the membrane fluidization . The latter results from an increased disorder of lipid molecules upon lipopeptide binding and/or insertion.…”

“…In all cases, the size of the L β domains is reduced and at the same time, the area occupied by L β is expanded, which is indicative of the membrane fluidization. 35 The latter results from an increased disorder of lipid molecules upon lipopeptide binding and/or insertion. This observation is in line with the results of the surface pressure measurement.…”

Ultrashort Cationic Lipopeptides–Effect of N-Terminal Amino Acid and Fatty Acid Type on Antimicrobial Activity and Hemolysis

“…Moreover, insertion of d-amino acids can be advantageous owing to enhanced protease stability. Change in configuration may result in different size of the peptide head-group and thus affect membrane fluidization [57,58]. Further studies should estimate toxicity of selected USCLs against different human cell lines and check the possibility of application of this idea to other lipopeptides, determine self-assembly characteristics, critical micellar concentration and peptide-membrane interactions, include quantitative structure-activity relationship (QSAR) studies, quantitative structure-toxicity relationship (QSTR), quantitative structure-retention relationship (QSRR) studies and molecular dynamics (MD) simulations to detect and identify interactions with bacterial, fungal and human cells membranes.…”

“…with Met(47)(48)(49)(50), Met(O)(51)(52)(53)(54), and Met(O2)(55)(56)(57)(58) represent another series of compounds. However, this one differs in the number of oxygen atoms in the side chain (0, 1, and 2, respectively).…”

Direct visualization of alamethicin ion pores formed in a floating phospholipid membrane supported on a gold electrode surface

“…where R is the radius of the tip curvature (10 nm), F is the average penetration force (0.3 nN) and E* is the effective compression modulus (6.6×10 7 N m -2 ), which is determined from the Young modulus of a bilayer in liquid crystalline state [30,37]. By applying Equation 1 to the collected force data, the elastic deformation of the film by the tip was estimated to be 1.2 nm.…”