How do Antimicrobial Peptides Interact with the Outer Membrane of Gram-Negative Bacteria? Role of Lipopolysaccharides in Peptide Binding, Anchoring, and Penetration.

Gram-negative bacteria possess a complex structural cell envelope that constitutes a barrier for antimicrobial peptides that neutralize the microbes by disrupting their cell membranes. Computational and experimental approaches were used to study a model outer membrane interaction with an antimicrobial peptide, melittin. The investigated membrane included di[3-deoxy-d-manno-octulosonyl]-lipid A (KLA) in the outer leaflet and 1-palmitoyl-2-oleoyl--glycero-3-phosphoethanolamine (POPE) in the inner leaflet.

Effects of Ethanolic Extract on the Proliferation and Viability of Melanoma Cells and Models of Their Cell Membranes.

is a fungus known for its medicinal properties. It possesses antimicrobial, anti-inflammatory, and anti-cancer activity. In this study, several tests were performed to evaluate the cytotoxic effect of the ethanolic extract of on two melanoma human cell lines, WM115 primary and A375 metastatic cell lines, as well as Hs27 human skin fibroblasts.

Membrane Potentials Trigger Molecular-Scale Rearrangements in the Outer Membrane of Gram-Negative Bacteria.

The structural complexity of the cell envelope of Gram-negative bacteria limits the fabrication of realistic models of bacterial cell membranes. A vertical Langmuir-Blodgett withdrawing was used to deposit a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) monolayer on the Au(111) surface. The second leaflet composed of di[3-deoxy-D-manno-octulosonyl]-lipid A (KLA) was deposited using Langmuir-Schaefer transfer.

The Ca response of a smart forisome protein is dependent on polymerization.

Forisomes are giant self-assembling mechanoproteins that undergo reversible structural changes in response to Ca and various other stimuli. Artificial forisomes assembled from the monomer MtSEO-F1 can be used as smart biomaterials, but the molecular basis of their functionality is not understood. To determine the role of protein polymerization in forisome activity, we tested the Ca association of MtSEO-F1 dimers (the basic polymerization unit) by circular dichroism spectroscopy and microscale thermophoresis.

Structural changes in the model of the outer cell membrane of Gram-negative bacteria interacting with melittin: an spectroelectrochemical study.

The cell membrane of Gram-negative bacteria interacting with an antimicrobial peptide presents a complex supramolecular assembly. Fabrication of models of bacterial cell membranes remains a large experimental challenge. Langmuir-Blodgett and Langmuir-Schaefer (LS-LB) transfer makes possible the deposition of multicomponent asymmetric lipid bilayers onto a gold surface.

CD Stretching Modes are Sensitive to the Microenvironment in Ionic Liquids.

Knowledge of the structure of the electrical double layer in ionic liquids (IL) is crucial for their applications in electrochemical technologies. We report the synthesis and applicability of an imidazolium-based amphiphilic ionic liquid with a perdeuterated alkyl chain for studies of electric potential-dependent rearrangements, and changes in the microenvironment in a monolayer on a Au(111) surface. Electrochemical measurements show two states of the organization of ions on the electrode surface.

Adsorption of lysozyme on gold surfaces in the presence of an external electric potential.

Adsorbed protein films consist of essential building blocks of many biotechnological and biomedical devices. The electrostatic potential may significantly modulate the protein behaviour on surfaces, affecting their structure and biological activity. In this study, lysozyme was used to investigate the effects of applied electric potentials on adsorption and the protein structure.

Electrochemical Activation of Self-Assembled Monolayers for the Binding of Effectors.

A self-assembled monolayer (SAM) on gold was prepared from a diaminoterephthalate (DAT) derivative as functional molecule and 1-decanthiol as a backfiller. The DAT derivative is -protected by a -butyloxycarbonyl (Boc) group and is anchored to the gold surface via a liponic acid as a stable anchor group. The terminal DAT moiety exhibits interesting effector properties such as fluorescence and electrochemical activity.

What Does Ectoine Do to DNA? A Molecular-Scale Picture of Compatible Solute-Biopolymer Interactions.

Compatible solutes accumulate in the cytoplasm of halophilic microorganisms, enabling their survival in a high-salinity environment. Ectoine is such a compatible solute. It is a zwitterionic molecule that strongly interacts with surrounding water molecules and changes the dynamics of the local hydration shell.

Pneumatic conveying printing technique for bioprinting applications.

Droplet-based bio-printing (DBB) techniques have been extensively accepted due to their simplicity, flexibility and cost performance. However, the applicability of inkjet printing for bioprinting techniques still faces challenges, such as a narrow range of available bio-ink materials, cell damage due to the pressure strike and high shear rate during the printing process. Here, a new droplet-based printing technique, pneumatic conveying printing (PCP), is described.

Binding of a Myristoylated Protein to the Lipid Membrane Influenced by Interactions with the Polar Head Group Region.

Many cytoplasmic proteins contain a hydrophobic acyl chain, which facilitates protein binding to cell membranes. Hydrophobic interactions between the exposed acyl chain of the protein and hydrocarbon chains of lipids in the cell membrane are the driving force for this specific lipid-protein interaction. Recent studies point out that in addition to hydrophobic interactions the charge-charge and charge-dipole interactions between the polar head groups and basic amino acids contribute significantly to the binding process.

Impact of the protein myristoylation on the structure of a model cell membrane in a protein bound state.

The neuronal calcium sensor protein recoverin is expressed in retinal rod and cone cells and is involved in the calcium-dependent control of receptor (rhodopsin) phosphorylation and receptor inactivation. In its Ca-saturated form recoverin is attached to membranes by an exposed myristoyl group and responds to oscillating changes of intracellular Ca-concentration by performing a so-called Ca-myristoyl switch. In this work we analyze changes in a liquid lipid bilayer interacting with myristoylated and non-myristoylated recoverin by employing polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) with electrochemical control.

An in situ spectroelectrochemical study on the orientation changes of an [FeL] metallosurfactant deposited as LB Films on gold electrode surfaces.

In this paper we analyze the changes in molecular orientation triggered by electrochemical reduction of an iron-containing surfactant in Langmuir-Blodgett films deposited onto gold electrodes. The metallosurfactant [Feiii(LN2O3)] (1) is an established molecular rectifier capable of unidirectional electron transfer between two electrodes. A gradual decrease in the activity is observed in sequential current vs.

Submolecular Structure and Orientation of Oligonucleotide Duplexes Tethered to Gold Electrodes Probed by Infrared Reflection Absorption Spectroscopy: Effect of the Electrode Potentials.

Unique electronic and ligand recognition properties of the DNA double helix provide basis for DNA applications in biomolecular electronic and biosensor devices. However, the relation between the structure of DNA at electrified interfaces and its electronic properties is still not well understood. Here, potential-driven changes in the submolecular structure of DNA double helices composed of either adenine-thymine (dAdT) or cytosine-guanine (dGdC) base pairs tethered to the gold electrodes are for the first time analyzed by in situ polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) performed under the electrochemical control.

Structure of collagen adsorbed on a model implant surface resolved by polarization modulation infrared reflection-absorption spectroscopy.

The polarization modulation infrared reflection-absorption spectra of collagen adsorbed on a titania surface and quantum chemical calculations are used to describe components of the amide I mode to the protein structure at a sub-molecular level. In this study, imino acid rich and poor fragments, representing the entire collagen molecule, are taken into account. The amide I mode of the collagen triple helix is composed of three absorption bands which involve: (i) (∼1690cm(-1)) the CO stretching modes at unhydrated groups, (ii) (1655-1673cm(-1)) the CO stretching at carbonyl groups at imino acids and glycine forming intramolecular hydrogen bonds with H atoms at both NH2 and, unusual for proteins, CH2 groups at glycine at a neighbouring chain and (iii) (∼1640cm(-1)) the CO stretching at carbonyl groups forming hydrogen bonds between two, often charged, amino acids as well as hydrogen bonds to water along the entire helix.

A Langmuir monolayer study of the action of phospholipase A2 on model phospholipid and mixed phospholipid-GM1 ganglioside membranes.

Polarization-modulation infrared reflection-absorption spectroscopy, surface pressure measurements and thermodynamic analysis were used to study enzymatic hydrolysis of lipid monolayers at the air/water interface. The Ca(2+)-requiring pork pancreatic phospholipase A2 was used as a catalyst. The substrates were pure 1,2-dilauroyl-sn-glycero-3-phosphocholine or mixed 1,2-dilauroyl-sn-glycero-3-phosphocholine - monosialotetrahexosylganglioside Langmuir films.

Local control of protein binding and cell adhesion by patterned organic thin films.

Control of the cell adhesion and growth on chemically patterned surfaces is important in an increasing number of applications in biotechnology and medicine, for example implants, in-vitro cellular assays, and biochips. This review covers patterning techniques for organic thin films suitable for site-directed guidance of cell adhesion to surfaces. Available surface patterning techniques are critically evaluated, with special emphasis on surface chemistry that can be switched in time and space during cultivation of cells.

Impact of strong and weak lipid-protein interactions on the structure of a lipid bilayer on a gold electrode surface.

A lipid bilayer deposited on an electrode surface can serve as a benchmark system to investigate lipid-protein interactions in the presence of physiological electric fields. Recoverin and myelin-associated glycoprotein (MAG) are used to study the impact of strong and weak protein-lipid interactions on the structure of model lipid bilayers, respectively. The structural changes in lipid bilayers are followed using electrochemical polarization modulation infrared reflection-absorption spectroscopy (PM IRRAS).

Orientation of the GM1 ganglioside in Langmuir-Blodgett monolayers: a PM IRRAS and computational study.

The GM1 ganglioside in the monolayer at the air/water interface shows a liquid expanded-liquid condensed phase transition. Due to a combination of the PM IRRAS results with quantum chemical calculations the structure and orientation of the GM1 molecule in the monolayer on the sub-molecular level is provided. The PM IRRAS studies of GM1 monolayers demonstrate that the phase transition is accompanied by a reorientation of sugar residues with simultaneous changes in the network of hydrogen bonds.

Structural analysis of HS(CD(2))(12)(O-CH(2)-CH(2))(6)OCH(3) monolayers on gold by means of polarization modulation infrared reflection absorption spectroscopy. progress of the reaction with bromine.

A self-assembled monolayer (SAM) on gold was formed with specifically perdeuterated hexaethylene glycol-terminated alkanethiol HS(CD(2))(12)(O-CH(2)-CH(2))(6)OCH(3) (D-OEG). The structure of the d-alkane and the oligoethylene glycol (OEG) parts of the molecule in a SAM was studied by means of polarization modulation infrared reflection absorption spectroscopy. The D-OEG monolayers are highly ordered and exist in a crystalline phase.