bilayer thickness Dotaz Zobrazit nápovědu
Treatment of complete loss of skin thickness requires expensive cellular materials and limited skin grafts used as temporary coverage. This paper presents an acellular bilayer scaffold modified with polydopamine (PDA), which is designed to mimic a missing dermis and a basement membrane (BM). The alternate dermis is made from freeze-dried collagen and chitosan (Coll/Chit) or collagen and a calcium salt of oxidized cellulose (Coll/CaOC). Alternate BM is made from electrospun gelatin (Gel), polycaprolactone (PCL), and CaOC. Morphological and mechanical analyzes have shown that PDA significantly improved the elasticity and strength of collagen microfibrils, which favorably affected swelling capacity and porosity. PDA significantly supported and maintained metabolic activity, proliferation, and viability of the murine fibroblast cell lines. The in vivo experiment carried out in a domestic Large white pig model resulted in the expression of pro-inflammatory cytokines in the first 1-2 weeks, giving the idea that PDA and/or CaOC trigger the early stages of inflammation. Otherwise, in later stages, PDA caused a reduction in inflammation with the expression of the anti-inflammatory molecule IL10 and the transforming growth factor β (TGFβ1), which could support the formation of fibroblasts. Similarities in treatment with native porcine skin suggested that the bilayer can be used as an implant for full-thickness skin wounds and thus eliminate the use of skin grafts.
- Klíčová slova
- Bilayer, Chitosan, Collagen, Oxidized cellulose, Polydopamine, Wound healing,
- MeSH
- myši MeSH
- nanovlákna * MeSH
- prasata MeSH
- sloučeniny osmia MeSH
- zánět MeSH
- zvířata MeSH
- Check Tag
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- chloropentaammineosmium(III) chloride MeSH Prohlížeč
- polydopamine MeSH Prohlížeč
- sloučeniny osmia MeSH
Small hydrophobic gold nanoparticles with diameter lower than the membrane thickness can form clusters or uniformly distribute within the hydrophobic core of the bilayer. The coexistence of two stable phases (clustered and dispersed) indicates the energy barrier between nanoparticles. We calculated the distance dependence of the membrane-mediated interaction between two adjacent nanoparticles. In our model we consider two deformation modes: the monolayer bending and the hydroxycarbon chain stretching. Existence of an energy barrier between the clustered and the separated state of nanoparticles was predicted. Variation analysis of the membrane mechanical parameters revealed that the energy barrier between two membrane embedded nanoparticles is mainly the consequence of the bending deformation and not change of the thickness of the bilayer in the vicinity of nanoparticles. It is shown, that the forces between the nanoparticles embedded in the biological membrane could be either attractive or repulsive, depending on the mutual distance between them.
- MeSH
- chemické modely * MeSH
- hydrofobní a hydrofilní interakce MeSH
- kovové nanočástice chemie MeSH
- lipidové dvojvrstvy chemie MeSH
- shluková analýza MeSH
- termodynamika MeSH
- zlato chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- lipidové dvojvrstvy MeSH
- zlato MeSH
Lipid nanodiscs are small synthetic lipid bilayer structures that are stabilized in solution by special circumscribing (or scaffolding) proteins or polymers. Because they create native-like environments for transmembrane proteins, lipid nanodiscs have become a powerful tool for structural determination of this class of systems when combined with cryo-electron microscopy or nuclear magnetic resonance. The elastic properties of lipid bilayers determine how the lipid environment responds to membrane protein perturbations, and how the lipid in turn modifies the conformational state of the embedded protein. However, despite the abundant use of nanodiscs in determining membrane protein structure, the elastic material properties of even pure lipid nanodiscs (i.e., without embedded proteins) have not yet been quantitatively investigated. A major hurdle is due to the inherently nonlocal treatment of the elastic properties of lipid systems implemented by most existing methods, both experimental and computational. In addition, these methods are best suited for very large "infinite" size lipidic assemblies, or ones that contain periodicity, in the case of simulations. We have previously described a computational analysis of molecular dynamics simulations designed to overcome these limitations, so it allows quantification of the bending rigidity (KC) and tilt modulus (κt) on a local scale even for finite, nonperiodic systems, such as lipid nanodiscs. Here we use this computational approach to extract values of KC and κt for a set of lipid nanodisc systems that vary in size and lipid composition. We find that the material properties of lipid nanodiscs are different from those of infinite bilayers of corresponding lipid composition, highlighting the effect of nanodisc confinement. Nanodiscs tend to show higher stiffness than their corresponding macroscopic bilayers, and moreover, their material properties vary spatially within them. For small-size MSP1 nanodiscs, the stiffness decreases radially, from a value that is larger in their center than the moduli of the corresponding bilayers by a factor of ∼2-3. The larger nanodiscs (MSP1E3D1 and MSP2N2) show milder spatial changes of moduli that are composition dependent and can be maximal in the center or at some distance from it. These trends in moduli correlate with spatially varying structural properties, including the area per lipid and the nanodisc thickness. Finally, as has previously been reported, nanodiscs tend to show deformations from perfectly flat circular geometries to varying degrees, depending on size and lipid composition. The modulations of lipid elastic properties that we find should be carefully considered when making structural and functional inferences concerning embedded proteins.
- MeSH
- elektronová kryomikroskopie MeSH
- lipidové dvojvrstvy * MeSH
- membránové proteiny MeSH
- nanostruktury * MeSH
- simulace molekulární dynamiky MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Názvy látek
- lipidové dvojvrstvy * MeSH
- membránové proteiny MeSH
In an effort to delineate how cholesterol protects membrane structure under oxidative stress conditions, we monitored the changes to the structure of lipid bilayers comprising 30 mol% cholesterol and an increasing concentration of Class B oxidized 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) glycerophospholipids, namely, 1-palmitoyl-2-(9'-oxo-nonanoyl)-sn-glycero-3-phosphocholine (PoxnoPC), and 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine (PazePC), using atomistic molecular dynamics simulations. Increasing the content of oxidized phospholipids (oxPLs) from 0 to 60 mol% oxPL resulted in a characteristic reduction in bilayer thickness and increase in area per lipid, thereby increasing the exposure of the membrane hydrophobic region to water. However, cholesterol was observed to help reduce water injury by moving into the bilayer core and forming more hydrogen bonds with the oxPLs. Cholesterol also resists altering its tilt angle, helping to maintain membrane integrity. Water that enters the 1-nm-thick core region remains part of the bulk water on either side of the bilayer, with relatively few water molecules able to traverse through the bilayer. In cholesterol-rich membranes, the bilayer does not form pores at concentrations of 60 mol% oxPL as was shown in previous simulations in the absence of cholesterol.
- Klíčová slova
- Cholesterol protection, Lipid oxidation, Oxidative stress, Oxidized membranes, Pore formation,
- MeSH
- cholesterol chemie metabolismus MeSH
- fosfatidylcholiny chemie metabolismus MeSH
- fosfolipidy chemie metabolismus MeSH
- fosforylcholin analogy a deriváty chemie metabolismus MeSH
- lipidové dvojvrstvy chemie metabolismus MeSH
- oxidace-redukce MeSH
- oxidační stres MeSH
- simulace molekulární dynamiky MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- 1-palmitoyl-2-azelaoyl-sn-glycero-3-phosphocholine MeSH Prohlížeč
- 1-palmitoyl-2-oleoylphosphatidylcholine MeSH Prohlížeč
- cholesterol MeSH
- fosfatidylcholiny MeSH
- fosfolipidy MeSH
- fosforylcholin MeSH
- lipidové dvojvrstvy MeSH
Conjugated dienes (CD) and thiobarbituric acid reactive substances (TBARS) have been estimated during the autoperoxidation of chromatographically pure phosphatidylcholine from hen eggs (EYPC) in multilamellar liposomes by UV-VIS spectrophotometry. During the propagation phase of autoperoxidation reaction, n-decane (C10) and n-octadecane (C18) gradually inhibit EYPC peroxidation up to 0:2:1 and 1:1 alkane:EYPC molar ratios, respectively. At higher molar ratios, the yield of estimated autoperoxidation products increases. At the highest molar ratio studied (alkane:EYPC = 2:1), the CD and TBARS concentrations exceed their levels in control sample without alkane added. The changes in the lipid bilayer thickness estimated from the small-angle neutron scattering (SANS) curves of unilamellar dioleoylphosphatidylcholine (DOPC) liposomes have indicated that C10 is located in the bilayer hydrophobic region parallel to the DOPC acyl chains at low molar ratios (C10:DOPC < or = 0.4). At higher molar ratios (0.6 < or = C10:DOPC < or = 1.0), the alkane changes its location into the center of the bilayer between the apposing monolayers. The alkane location parallel to polyunsaturated lipid fatty acyl chains RH separates these chains resulting in a decreased frequency of their encounters, in decreased yields of ROO. + RH-->ROOH + R., 2 ROOH-->RO. + ROO. + H2O and RO. + RH-->R. + ROH free radical reactions, and consequently, in decreased autoperoxidation. Autoperoxidation returns to the control values due to alkane redistribution into the bilayer center. 1H decoupled 31P NMR spectra of EYPC + C10 aqueous dispersions have shown that the lipid bilayer transforms into nonbilayer phases at C10:EYPC > 1:1 molar ratios. The inverted hexagonal HII phase with C10 (or C18) preferentially located in the interstitial regions of the HII unit cell displays higher autoperoxidation than the control bilayer sample due to greater motional freedom of RH chains in the HII phase.
- MeSH
- alkany * MeSH
- fosfatidylcholiny analýza chemie MeSH
- kur domácí MeSH
- lipidové dvojvrstvy MeSH
- liposomy * MeSH
- peroxidace lipidů * MeSH
- vaječný žloutek chemie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- anglický abstrakt MeSH
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- alkany * MeSH
- decane MeSH Prohlížeč
- fosfatidylcholiny MeSH
- lipidové dvojvrstvy MeSH
- liposomy * MeSH
- octadecane MeSH Prohlížeč
We assembled photoresponsive mono- and bilayer systems with well-defined properties from rod-shaped molecules equipped with different photoswitches. Using properly chosen chromophores (diarylethene-based switch and unidirectional light-driven molecular motor), we then selectively targeted layers made of the same types of photoswitches using appropriate monochromatic light. UV-vis analysis confirmed smooth and unrestricted photoisomerization. To achieve this, we synthesized a new class of triptycene-based molecular pedestals adept at forming sturdy Langmuir-Blodgett films on a water-air interface. The films were smoothly transferred to gold and quartz surfaces. Repeated deposition afforded bilayer systems: one layer containing diarylethene-based photoswitches and the other a unidirectional light-driven molecular motor. Structural analysis of both mono- and bilayer systems revealed the molecules to be tilted with carboxylic functions pointing to the surface. At least two different polymorphs differing in monolayer thickness and tilt angle (~40° and ~60°) were identified on the gold surface.
- Publikační typ
- časopisecké články MeSH
The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.
- Klíčová slova
- bilayer thickness, elasticity, flavonols, fluidity, lipid peroxidation, myricetin, myricitrin, quercetin,
- Publikační typ
- časopisecké články MeSH
The morphology and crystal structure of Pt films grown by pulsed laser deposition (PLD) on yttria-stabilized zirconia (YSZ)at high temperatures Tg = 900 °C was studied for four different film thicknesses varying between 10 and 70 nm. During the subsequent growth of the capping layer, the thermal stability of the Pt was strongly influenced by the Pt film's thickness. Furthermore, these later affected the film morphology, the crystal structure and hillocks size, and distribution during subsequent growth at Tg = 900 °C for a long duration. The modifications in the morphology as well as in the structure of the Pt film without a capping layer, named also as the as-grown and encapsulated layers in the bilayer system, were examined by a combination of microscopic and scattering methods. The increase in the thickness of the deposited Pt film brought three competitive phenomena into occurrence, such as 3D-2D morphological transition, dewetting, and hillock formation. The degree of coverage, film continuity, and the crystal quality of the Pt film were significantly improved by increasing the deposition time. An optimum Pt film thickness of 70 nm was found to be suitable for obtaining a hillock-free Pt bottom electrode which also withstood the dewetting phenomena revealed during the subsequent growth of capping layers. This achievement is crucial for the deposition of functional bottom electrodes in ferroelectric and multiferroic heterostructure systems.
- Klíčová slova
- PLD, X-ray diffraction, atomic force microscopy, bottom electrode, dewetting, electron microscopy, encapsulated platinum, hillock formation, platinum,
- Publikační typ
- časopisecké články MeSH
Here, we demonstrate the impact of ferromagnetic layer coating on controlling the magneto-optical response. We found that the transverse magneto-optical Kerr effect (TMOKE) signal and TMOKE hysteresis loops of Ni80Fe20 thin layers coated with a Cr layer show a strong dependence on the thickness of the Cr layer and the incidence angle of the light. The transmission and reflection spectra were measured over a range of incidence angles and with different wavelengths so as to determine the layers' optical parameters and to explain the TMOKE behavior. The generalized magneto-optical and ellipsometry (GMOE) model based on modified Abeles characteristic matrices was used to examine the agreement between the experimental and theoretical results. A comprehensive theoretical and experimental analysis reveals the possibility to create a TMOKE suppression/enhancement coating at specific controllable incidence angles. This has potential for applications in optical microscopy and sensors.
Using x-ray magnetic circular and linear dichroism techniques, we demonstrate a collinear exchange coupling between an epitaxial antiferromagnet, tetragonal CuMnAs, and an Fe surface layer. A small uncompensated Mn magnetic moment is observed which is antiparallel to the Fe magnetization. The staggered magnetization of the 5 nm thick CuMnAs layer is rotatable under small magnetic fields, due to the interlayer exchange coupling. This allows us to obtain the x-ray magnetic linear dichroism spectra for different crystalline orientations of CuMnAs in the (001) plane. This is a key parameter for enabling the understanding of domain structures in CuMnAs imaged using x-ray magnetic linear dichroism microscopy techniques.
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
