scholarly journals Molecular Transport and Growth of Lipid Vesicles Exposed to Antimicrobial Peptides

Langmuir ◽  
2021 ◽  
Author(s):  
Josefine Eilsø Nielsen ◽  
Reidar Lund
Keyword(s):  
Antimicrobial Peptides ◽  
Molecular Transport ◽  
Lipid Vesicles

scholarly journals Molecular Transport across Lipid Membranes Controls Cell-Free Expression Level and Dynamics

2019 ◽  
Author(s):  
Patrick M. Caveney ◽  
Rosemary M. Dabbs ◽  
William T. McClintic ◽  
C. Patrick Collier ◽  
Michael L. Simpson
Keyword(s):  
Gene Expression ◽  
Membrane Transport ◽  
Molecular Species ◽  
Lipid Membranes ◽  
Molecular Transport ◽  
Lipid Vesicles ◽  
Cellular Systems ◽  
Control Of Gene Expression ◽  
External Resources ◽  
Synthetic Cell

SummaryEssential steps toward synthetic cell-like systems require controlled transport of molecular species across the boundary between encapsulated expression and the external environment. When molecular species (e.g. small ions, amino acids) required for expression (i.e. expression resources) may cross this boundary, this transport process plays an important role in gene expression dynamics and expression variability. Here we show how the location (encapsulated or external) of the expression resources controls the level and the dynamics of cell-free protein expression confined in permeable lipid vesicles. Regardless of the concentration of encapsulated resources, external resources were essential for protein production. Compared to resource poor external environments, plentiful external resources increased expression by ~7-fold, and rescued expression when internal resources were lacking. Intriguingly, the location of resources and the membrane transport properties dictated expression dynamics in a manner well predicted by a simple transport-expression model. These results suggest membrane engineering as a means for spatio-temporal control of gene expression in cell-free synthetic biology applications and demonstrate a flexible experimental platform to understand the interplay between membrane transport and expression in cellular systems.

scholarly journals Magainin 2 and PGLa in Bacterial Membrane Mimics II: Membrane Fusion and Sponge Phase Formation

2019 ◽  
Author(s):  
Ivo Kabelka ◽  
Michael Pachler ◽  
Sylvain Prévost ◽  
Ilse Letofsky-Papst ◽  
Karl Lohner ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Defect Formation ◽  
Preceding Paper ◽  
Lipid Vesicles ◽  
Synergistic Activity ◽  
Electron Microscopic ◽  
Synergistic Mechanism ◽  
Sponge Phase ◽  
Lipid Aggregates ◽  
Dynamics Simulations

ABSTRACTWe studied the synergistic mechanism of equimolar mixtures of magainin 2 (MG2a) and PGLa in phosphatidylethanolamine/phosphatidylglycerol mimics of Gram-negative cytoplasmic membranes. In a preceding paper [Pachler et al., Biophys. J. 2019 xxx], we reported on the early onset of parallel heterodimer formation of the two antimicrobial peptides already at low concentrations and the resulting defect formation in membranes. Here, we focus on the structures of the peptide/lipid aggregates occurring in the synergistic regime at elevated peptide concentrations. Using a combination of calorimetric, scattering, electron microscopic and in silico techniques, we demonstrate that the two peptides, even if applied individually, transform originally large unilamellar vesicles into multilamellar vesicles, with a collapsed interbilayer spacing resulting from peptide induced adhesion. Interestingly, the adhesion does not lead to a peptide induced lipid separation of charged and charge neutral species. In addition to this behavior, equimolar mixtures of MG2a and PGLa formed surface-aligned fibril-like structures, which induced adhesion zones between the membranes and the formation of transient fusion stalks in molecular dynamics simulations and a coexisting sponge phase observed by small-angle X-ray scattering. The previously reported increased leakage of lipid vesicles of identical composition in the presence of MG2a/PGLa mixtures is therefore related to a peptide-induced cross-linking of bilayers.STATEMENT OF SIGNIFICANCEWe demonstrate that the synergistic activity of the antimicrobial peptides MG2a and PGLa correlates to the formation of surface-aligned fibril-like peptide aggregates, which cause membrane adhesion, fusion and finally the formation of a sponge phase.

scholarly journals Antimicrobial Activities and Structures of Two Linear Cationic Peptide Families with Various Amphipathic β-Sheet and α-Helical Potentials

2005 ◽  
Vol 49 (12) ◽  
pp. 4957-4964 ◽  
Author(s):  
Yi Jin ◽  
Janet Hammer ◽  
Michelle Pate ◽  
Yu Zhang ◽  
Fang Zhu ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Antimicrobial Peptides ◽  
Plasma Membranes ◽  
Membrane Lipids ◽  
Lipid Vesicles ◽  
Selective Advantage ◽  
Antimicrobial Activities ◽  
Helical Conformation ◽  
Bacterial Cells ◽  
Β Sheet

ABSTRACT Many naturally occurring antimicrobial peptides comprise cationic linear sequences with the potential to adopt an amphipathic α-helical conformation. We designed a linear 18-residue peptide that adopted an amphipathic β-sheet structure when it was bound to lipids. In comparison to a 21-residue amphipathic α-helical peptide of equal charge and hydrophobicity, this peptide possessed more similar antimicrobial activity and greater selectivity in binding to and inducing leakage in vesicles composed of bacterial membrane lipids than vesicles composed of mammalian membrane lipids (J. Blazyk, R. Weigand, J. Klein, J. Hammer, R. M. Epand, R. F. Epand, W. L. Maloy, and U. P. Kari, J. Biol. Chem. 276:27899-27906, 2001). Here, we compare two systematically designed families of linear cationic peptides to evaluate the importance of amphipathicity for determination of antimicrobial activity. Each peptide contains six lysine residues and is amidated at the carboxyl terminus. The first family consists of five peptides with various capacities to form amphipathic β-sheet structures. The second family consists of six peptides with various potentials to form amphipathic α helices. Only those peptides that can form a highly amphipathic structure (either a β sheet or an α helix) possessed significant antimicrobial activities. Striking differences in the abilities to bind to and induce leakage in membranes and lipid vesicles were observed for the two families. Overall, the amphipathic β-sheet peptides are less lytic than their amphipathic α-helical counterparts, particularly toward membranes containing phosphatidylcholine, a lipid commonly found in mammalian plasma membranes. Thus, it appears that antimicrobial peptides that can form an amphipathic β-sheet conformation may offer a selective advantage in targeting bacterial cells.

scholarly journals Antimicrobial Peptides: Correlation Between Pore Forming Potency in Lipid Vesicles and Antimicrobial, Hemolytic and Cytotoxic Activity

2012 ◽  
Vol 102 (3) ◽  
pp. 90a-91a
Author(s):  
Jing He ◽  
Aram Krauson ◽  
Andrew W. Wimley ◽  
Andrew R. Hoffmann ◽  
William Wimley
Keyword(s):  
Antimicrobial Peptides ◽  
Cytotoxic Activity ◽  
Lipid Vesicles

Inducing toxicity by introducing a leucine-zipper-like motif in frog antimicrobial peptide, magainin 2

2011 ◽  
Vol 436 (3) ◽  
pp. 609-620 ◽  
Author(s):  
Brijesh Kumar Pandey ◽  
Saurabh Srivastava ◽  
Manish Singh ◽  
Jimut Kanti Ghosh
Keyword(s):  
Antimicrobial Peptides ◽  
Mammalian Cells ◽  
Leucine Zipper ◽  
Lipid Vesicles ◽  
Aqueous Environment ◽  
Structural Element ◽  
Human Red Blood Cells ◽  
Naturally Occurring ◽  
Hydrophobic Amino Acids

Cytotoxicity, a major obstacle in therapeutic application of antimicrobial peptides, is controlled by leucine-zipper-like sequences in melittin and other naturally occurring antimicrobial peptides. Magainin 2 shows significantly lower cytotoxicity than many naturally occurring antimicrobial peptides and lacks this structural element. To investigate the consequences of introducing a leucine zipper sequence in magainin 2, a novel analogue (Mag-mut) was designed by rearranging only the positions of its hydrophobic amino acids to include this structural element. Both magainin 2 and Mag-mut showed appreciable similarities in their secondary structures in the presence of negatively charged lipid vesicles, in localizing and permeabilizing the selected bacteria and exhibiting bactericidal activities. However, Mag-mut bound and localized strongly on to the mammalian cells tested and exhibited significantly higher cytotoxicity than magainin 2. Only Mag-mut, but not magainin 2, permeabilized human red blood cells and zwitterionic lipid vesicles. In contrast with magainin 2, Mag-mut self-assembled in an aqueous environment and bound co-operatively on to zwitterionic lipid vesicles. The peptides formed pores of different sizes on to a selected mammalian cell. The results of the present study indicate an important role of the leucine zipper sequence in the cytotoxicity of Mag-mut and demonstrate that its introduction into a non-toxic peptide, without altering the amino acid composition, can render cytotoxicity.

Cryo-electron and optical microscopy study of lipid-encapsulated microtubules

1995 ◽  
Vol 53 ◽  
pp. 712-713
Author(s):  
M. E. Bisher ◽  
D. K. Fygensont ◽  
F. Booy ◽  
A. Libchabert ◽  
M. M. J. Treacy
Keyword(s):  
Optical Microscopy ◽  
Dynamic Instability ◽  
Genetic Material ◽  
Molecular Transport ◽  
Lipid Vesicles ◽  
Microscopy Study ◽  
Eukaryotic Cell ◽  
Lipid Vesicle ◽  
Cellular Processes ◽  
Optical Micrograph

The dimeric protein tubulin is found in every eukaryotic cell. In the presence of GTP and Mg++ cations, tubulin polymerizes into long hollow cylinders known as microtubules, that are 24 nm in diameter and can grow as long as 10-100 μm in length. Microtubules play an important role in living cells: they act as guides for internal molecular transport (most notably the separation of genetic material during anaphase in cell division), they are a major component of the cytoskeleton, and are important structural constituents of cilia and flagellae. Locomotion, morphogenesis and reproduction, are fundamental cellular processes that rely on the polymerization of microtubules and on their ability to re-organize - a feature termed dynamic instability.Tubulin, purified from fresh cow brain, exhibits this dynamic instability in the laboratory in the absence of microtubule-associated protein. Length fluctuations can be observed by differential interference contrast (DIC) optical microscopy. The instability persists when tubulin is encapsulated in lipid vesicles (liposomes), formed by adding the phospholipids DOPC and DOPS, and applying the freeze-thaw technique to the mixture. Fig. 1 shows a DIC optical micrograph of a ˜5 (im lipid vesicle that is distorted, or impaled, by a 12 μm rod which is presumably a microtubule, or a bundle of microtubules. Frequently, such microtubules are observed to buckle because of reaction forces from the membrane.

scholarly journals A microfluidic platform for the characterisation of membrane active antimicrobials

Lab on a Chip ◽  
2019 ◽  
Vol 19 (5) ◽  
pp. 837-844 ◽  
Author(s):  
K. Al Nahas ◽  
J. Cama ◽  
M. Schaich ◽  
K. Hammond ◽  
S. Deshpande ◽  
...  
Keyword(s):  
Antimicrobial Peptides ◽  
Lipid Vesicles ◽  
Microfluidic Platform ◽  
Total Analysis System ◽  
System P ◽  
Total Analysis ◽  
Analysis System

We quantify the membranolytic activity of antimicrobial peptides on biomimetic lipid vesicles in a multilayer microfluidic total analysis system.

scholarly journals Length Effects in Antimicrobial Peptides of the (RW)n Series

2006 ◽  
Vol 51 (2) ◽  
pp. 597-603 ◽  
Author(s):  
Zhigang Liu ◽  
Anna Brady ◽  
Anne Young ◽  
Brian Rasimick ◽  
Kang Chen ◽  
...  
Keyword(s):  
Antimicrobial Activity ◽  
Antimicrobial Peptides ◽  
Chain Length ◽  
Host Defense ◽  
Hemolytic Activity ◽  
Blood Cells ◽  
Experimental Error ◽  
Tryptophan Fluorescence ◽  
Lipid Vesicles ◽  
Simple Sequence

ABSTRACT A class of antimicrobial peptides involved in host defense consists of sequences rich in Arg and Trp-R and -W. Analysis of the pharmacophore in these peptides revealed that chains as short as trimers of sequences such as WRW and RWR have antimicrobial activity (M. B. Strom, B. E. Haug, M. L. Skar, W. Stensen, T. Stiberg, and J. S. Svendsen, J. Med. Chem. 46:1567-1570, 2003). To evaluate the effect of chain length on antimicrobial activity, we synthesized a series of peptides containing simple sequence repeats, (RW) n -NH2 (where n equals 1, 2, 3, 4, or 5), and determined their antimicrobial and hemolytic activity. The antimicrobial activity of the peptides increases with chain length, as does the hemolysis of red blood cells. Within the experimental error, longer peptides (n equals 3, 4, or 5) show similar values for the ratio of hemolytic activity to antibacterial activity, or the hemolytic index. The (RW)3 represents the optimal chain length in terms of the efficacy of synthesis and selectivity as evaluated by the hemolytic index. Circular dichroism spectroscopy indicates that these short peptides appear to be unfolded in aqueous solution but acquire structure in the presence of phospholipids. Interaction of the peptides with model lipid vesicles was examined using tryptophan fluorescence. The (RW) n peptides preferentially interact with bilayers containing the negatively charged headgroup phosphatidylglycerol relative to those containing a zwitterionic headgroup, phosphatidylcholine.

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