Two cations, two mechanisms : interactions of sodium and calcium with zwitterionic lipid membranes

Adsorption of metal cations onto a cellular membrane changes its properties, such as interactions with charged moieties or the propensity for membrane fusion. It is, however, unclear whether cells can regulate ion adsorption and the related functions via locally adjusting their membrane composition. We employed fluorescence techniques and computer simulations to determine how the presence of cholesterol-a key molecule inducing membrane heterogeneity-affects the adsorption of sodium and calcium onto zwitterionic phosphatidylcholine bilayers. We found that the transient adsorption of sodium is dependent on the number of phosphatidylcholine head groups, while the strong surface binding of calcium is determined by the available surface area of the membrane. Cholesterol thus does not affect sodium adsorption and only plays an indirect role in modulating the adsorption of calcium by increasing the total surface area of the membrane. These observations also indicate how lateral lipid heterogeneity can regulate various ion-induced processes including adsorption of peripheral proteins, nanoparticles, and other molecules onto membranes.Peer reviewe

Freestanding non-covalent thin films of the propeller-shaped polycyclic aromatic hydrocarbon decacyclene

Molecularly thin, nanoporous thin films are of paramount importance in material sciences. Their use in a wide range of applications requires control over their chemical functionalities, which is difficult to achieve using current production methods. Here, the small polycyclic aromatic hydrocarbon decacyclene is used to form molecular thin films, without requiring covalent crosslinking of any kind. The 2.5 nm thin films are mechanically stable, able to be free-standing over micrometer distances, held together solely by supramolecular interactions. Using a combination of computational chemistry and microscopic imaging techniques, thin films are studied on both a molecular and microscopic scale. Their mechanical strength is quantified using AFM nanoindentation, showing their capability of withstanding a point load of 26 ± 9 nN, when freely spanning over a 1 μm aperture, with a corresponding Young’s modulus of 6 ± 4 GPa. Our thin films constitute free-standing, non-covalent thin films based on a small PAH

Lateral membrane organization as target of an antimicrobial peptidomimetic compound

Antimicrobial resistance is one of the leading concerns in medical care. Here we study the mechanism of action of an antimicrobial cationic tripeptide, AMC-109, by combining high speed-atomic force microscopy, molecular dynamics, fluorescence assays, and lipidomic analysis. We show that AMC-109 activity on negatively charged membranes derived from Staphylococcus aureus consists of two crucial steps. First, AMC-109 self-assembles into stable aggregates consisting of a hydrophobic core and a cationic surface, with specificity for negatively charged membranes. Second, upon incorporation into the membrane, individual peptides insert into the outer monolayer, affecting lateral membrane organization and dissolving membrane nanodomains, without forming pores. We propose that membrane domain dissolution triggered by AMC-109 may affect crucial functions such as protein sorting and cell wall synthesis. Our results indicate that the AMC-109 mode of action resembles that of the disinfectant benzalkonium chloride (BAK), but with enhanced selectivity for bacterial membranes.</p

Teixobactin kills bacteria by a two-pronged attack on the cell envelope

Antibiotics that use novel mechanisms are needed to combat antimicrobial resistance1–3. Teixobactin4 represents a new class of antibiotics with a unique chemical scaffold and lack of detectable resistance. Teixobactin targets lipid II, a precursor of peptidoglycan5. Here we unravel the mechanism of teixobactin at the atomic level using a combination of solid-state NMR, microscopy, in vivo assays and molecular dynamics simulations. The unique enduracididine C-terminal headgroup of teixobactin specifically binds to the pyrophosphate-sugar moiety of lipid II, whereas the N terminus coordinates the pyrophosphate of another lipid II molecule. This configuration favours the formation of a β-sheet of teixobactins bound to the target, creating a supramolecular fibrillar structure. Specific binding to the conserved pyrophosphate-sugar moiety accounts for the lack of resistance to teixobactin4. The supramolecular structure compromises membrane integrity. Atomic force microscopy and molecular dynamics simulations show that the supramolecular structure displaces phospholipids, thinning the membrane. The long hydrophobic tails of lipid II concentrated within the supramolecular structure apparently contribute to membrane disruption. Teixobactin hijacks lipid II to help destroy the membrane. Known membrane-acting antibiotics also damage human cells, producing undesirable side effects. Teixobactin damages only membranes that contain lipid II, which is absent in eukaryotes, elegantly resolving the toxicity problem. The two-pronged action against cell wall synthesis and cytoplasmic membrane produces a highly effective compound targeting the bacterial cell envelope. Structural knowledge of the mechanism of teixobactin will enable the rational design of improved drug candidates

Ions modulate stress-induced nano-texture in supported fluid lipid bilayers.

Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of ∼20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membrane’s properties on a length scale of ∼20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton

Teixobactin kills bacteria by a two-pronged attack on the cell envelope

Antibiotics that use novel mechanisms are needed to combat antimicrobial resistance1–3. Teixobactin4 represents a new class of antibiotics with a unique chemical scaffold and lack of detectable resistance. Teixobactin targets lipid II, a precursor of peptidoglycan5. Here we unravel the mechanism of teixobactin at the atomic level using a combination of solid-state NMR, microscopy, in vivo assays and molecular dynamics simulations. The unique enduracididine C-terminal headgroup of teixobactin specifically binds to the pyrophosphate-sugar moiety of lipid II, whereas the N terminus coordinates the pyrophosphate of another lipid II molecule. This configuration favours the formation of a β-sheet of teixobactins bound to the target, creating a supramolecular fibrillar structure. Specific binding to the conserved pyrophosphate-sugar moiety accounts for the lack of resistance to teixobactin4. The supramolecular structure compromises membrane integrity. Atomic force microscopy and molecular dynamics simulations show that the supramolecular structure displaces phospholipids, thinning the membrane. The long hydrophobic tails of lipid II concentrated within the supramolecular structure apparently contribute to membrane disruption. Teixobactin hijacks lipid II to help destroy the membrane. Known membrane-acting antibiotics also damage human cells, producing undesirable side effects. Teixobactin damages only membranes that contain lipid II, which is absent in eukaryotes, elegantly resolving the toxicity problem. The two-pronged action against cell wall synthesis and cytoplasmic membrane produces a highly effective compound targeting the bacterial cell envelope. Structural knowledge of the mechanism of teixobactin will enable the rational design of improved drug candidates

Teixobactin kills bacteria by a two-pronged attack on the cell envelope

Antibiotics that use novel mechanisms are needed to combat antimicrobial resistance1–3. Teixobactin4 represents a new class of antibiotics with a unique chemical scaffold and lack of detectable resistance. Teixobactin targets lipid II, a precursor of peptidoglycan5. Here we unravel the mechanism of teixobactin at the atomic level using a combination of solid-state NMR, microscopy, in vivo assays and molecular dynamics simulations. The unique enduracididine C-terminal headgroup of teixobactin specifically binds to the pyrophosphate-sugar moiety of lipid II, whereas the N terminus coordinates the pyrophosphate of another lipid II molecule. This configuration favours the formation of a β-sheet of teixobactins bound to the target, creating a supramolecular fibrillar structure. Specific binding to the conserved pyrophosphate-sugar moiety accounts for the lack of resistance to teixobactin4. The supramolecular structure compromises membrane integrity. Atomic force microscopy and molecular dynamics simulations show that the supramolecular structure displaces phospholipids, thinning the membrane. The long hydrophobic tails of lipid II concentrated within the supramolecular structure apparently contribute to membrane disruption. Teixobactin hijacks lipid II to help destroy the membrane. Known membrane-acting antibiotics also damage human cells, producing undesirable side effects. Teixobactin damages only membranes that contain lipid II, which is absent in eukaryotes, elegantly resolving the toxicity problem. The two-pronged action against cell wall synthesis and cytoplasmic membrane produces a highly effective compound targeting the bacterial cell envelope. Structural knowledge of the mechanism of teixobactin will enable the rational design of improved drug candidates

Recording at studio from comprehensive and educational perspective of interpreteur (at Sono Records)

The work deals with the preparation of recording and recording itself. It is intended for beginning musicians. It is divided into two basic parts, which are divided into other smaller compartments. The first part focuses on preparation for recording and discusses the selection of materials, solving various points such as lyrics, music, instrument preparation and other tasks. It also focuses on the selection of the recording studio and in which cases is suitable to use a work of producer. It also describes work of producers in Czech Republic. Part of it is also dedicated to the distribution, promotion, and financial aspects of the recording. Last but not least, it is trying to explain how to plan the whole project. It relies primarily on sources arising from consultations, as this issue is not sufficiently covered in the literature. The second part deals with recording. It is focused on the recording process of the band and at the same time shows the peculiarities of the interpretation at studio. The chapters contains examples of interesting recording techniques and comparisons of recording in the Czech Republic and abroad. Recording goes through all phases - sound check, recording, mix and mastering. At the end, it evaluates the information and related resources, demonstrates problems with solving..

AFM images and AFM force curves characterizing S. aureus lipid membrane upon interaction with antimicrobial peptidomimetic AMC-109, Mass Spectroscopy data of S. aureus lipid extracts: Experimental data for Lateral membrane organization as target of an antimicrobial peptidomimetic compound 2023

Atomic force microscopy (AFM) data characterizing the interaction of antimicrobial peptidomimetic AMC-109 with the lipid membrane extracted from bacteria Staphylococcus aureus. All experiments were done on membranes deposited on mica surface in PBS buffer at room temperature. AFM data were measured using JPK Nano Wizard Ultra Speed AFM. AFM raw images are presented in their JPK software format. Each AFM force-distance curve was calibrated according to a hard-response calibrating curve collected prior to each indentation of the membrane. These calibrated curves were exported in TXT format. Each TXT file contains 2 data sets corresponding to the approach and retract force-indentation curve one after another, organized in 2 columns showing "Vertical Tip Position" and "Vertical Deflection". Mass Spectroscopy data of S. aureus lipid extracts in their raw format gathered using an Ultra-high performance liquid chromatography-mass spectroscopy instrument consisting of Accela1250 UHPLC system (Thermo Fisher Scientific) coupled to a Thermo Exactive Orbitrap mass spectrometer (Thermo Fisher Scientific) equipped with an ESO ion-source in negative ionization mode. Detailed description of the individual folders: Folder "Figure 1": AFM raw images of S. aureus lipid membrane before and after step by step addition of antimicrobial peptidomimetic AMC-109. Folder "Figure S2": AFM raw images of S. aureus lipid membrane that is expanding in time after treatment with antimicrobial peptidomimetic AMC-109. Folder "Figure S3": AFM raw images of S. aureus lipid membrane before and after addition of antimicrobial peptidomimetic AMC-109 in a concentration above its minimal inhibitory concentration . Folder "Figure S5": AFM force-indentation curves gathered on S. aureus lipid membranes without any treatment and after treatment with subcritical concentrations of the antimicrobial AMC-109. The force-indentation curves were used to characterize the mechanical properties of the membrane upon the antibiotic treatment. The folder "Figure S5" contains three subfolders that contain individual force-indentation curves measured on S. aureus lipid membranes exposed to no AMC-109 (0_ug-ml_AMC-109), 0.5 ug/ml AMC-109 (0p5_ug-ml_AMC-109), and 1 ug/ml AMC-109 (1_ug-ml_AMC-109). Folder "Figure S7": AFM raw images of AMC-109 layer forming on the mica support. Mica was exposed to the PBS buffer with 2 ug/ml AMC-109, this layer was scratched by contact imaging with the AFM tip. The AFM images show the recovery of the AMC-109 layer on mica. Folder "Figure S14": AFM raw images of the S. aureus lipid membrane before and after the exposure to 0.023 vol% of DMSO. Folder "Table 1 and Figure S1": Mass Spectroscopy data of S. aureus lipid extracts in their raw format

Recording at studio from comprehensive and educational perspective of interpreteur (at Sono Records)

The work deals with the preparation of recording and recording itself. It is intended for beginning musicians. It is divided into two basic parts, which are divided into other smaller compartments. The first part focuses on preparation for recording and discusses the selection of materials, solving various points such as lyrics, music, instrument preparation and other tasks. It also focuses on the selection of the recording studio and in which cases is suitable to use a work of producer. It also describes work of producers in Czech Republic. Part of it is also dedicated to the distribution, promotion, and financial aspects of the recording. Last but not least, it is trying to explain how to plan the whole project. It relies primarily on sources arising from consultations, as this issue is not sufficiently covered in the literature. The second part deals with recording. It is focused on the recording process of the band and at the same time shows the peculiarities of the interpretation at studio. The chapters contains examples of interesting recording techniques and comparisons of recording in the Czech Republic and abroad. Recording goes through all phases - sound check, recording, mix and mastering. At the end, it evaluates the information and related resources, demonstrates problems with solving..