Search results for "bilayers"
showing 10 items of 140 documents
Unsaturated Fatty Acids Drive Disintegrin and Metalloproteinase (ADAM)-dependent Cell Adhesion, Proliferation, and Migration by Modulating Membrane F…
2011
The disintegrin-metalloproteinases ADAM10 and ADAM17 mediate the release of several cell signaling molecules and cell adhesion molecules such as vascular endothelial cadherin or L-selectin affecting endothelial permeability and leukocyte transmigration. Dysregulation of ADAM activity may contribute to the pathogenesis of vascular diseases, but the mechanisms underlying the control of ADAM functions are still incompletely understood. Atherosclerosis is characterized by lipid plaque formation and local accumulation of unsaturated free fatty acids (FFA). Here, we show that unsaturated FFA increase ADAM-mediated substrate cleavage. We demonstrate that these alterations are not due to genuine ch…
Pulmonary surfactant protein C containing lipid films at the air-water interface as a model for the surface of lung alveoli.
1995
The pulmonary surfactant lines as a complex monolayer of lipids and proteins the alveolar epithelial surface. The monolayer dynamically adapts the surface tension of this interface to the varying surface areas during inhalation and exhalation. Its presence in the alveoli is thus a prerequisite for a proper lung function. The lipid moiety represents about 90% of the surfactant and contains mainly dipalmitoylphosphatidylcholine (DPPC) and phosphatidylglycerol (PG). The surfactant proteins involved in the surface tension adaption are called SP-A, SP-B and SP-C. The aim of the present investigation is to analyse the properties of monolayer films made from pure SP-C and from mixtures of DPPC, DP…
Interactions of liposomes and hydrophobically-modified poly-(N-isopropylacrylamides): an attempt to model the cytoskeleton
1993
The interactions of small unilamellar vesicles (SUV) and water-soluble copolymers were studied by fluorescence spectroscopy, differential scanning calorimetry (DSC) and quasi-elastic light scattering (QELS). The anchoring onto liposomal bilayer membranes of copolymers of N-isopropylacrylamide, N-(2-(1-naphthyl)ethyl)-N-n-octadecylacrylamide and or N-[4-(1-pyrenyl)butyl]-N-n-octadecylacrylamide (0.5 mol% of the octadecylacrylamide comonomer) was monitored by non-radiative energy transfer between excited naphthalene and pyrene. The anchoring process occurred on zwitterionic lecithin liposomes and on negatively charged phosphatidic acid liposomes, whether the bilayer was in the crystalline or …
Spectrophotometric evidence for the solubilization site of betalain pigments in membrane biomimetic systems.
2007
The solubilization site of two betalain pigments, namely, betanin and indicaxantin, into l-alpha-dipalmitoyl-phosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) vesicles was investigated by a spectrophotometric study. Pigment absorbance was monitored by varying phospholipid concentration, at a constant temperature that was varied in a range including the main phase transition temperature (Tm) of the relevant phospholipid bilayer. Maximum betanin absorption increased with the increase of DPPC concentration within the entire temperature range, reaching a plateau. The binding constant (Kb) of the pigment, calculated according to a pseudo-two-phase model, varied with the temper…
Quantification of the Raf-C1 Interaction With Solid-Supported Bilayers
2002
By use of the quartz crystal microbalance technique, the interaction of the Raf-Ras binding domain (RafRBD) and the cysteine-rich domain Raf-C1 with lipids was quantified by using solid-supported bilayers immobilized on gold electrodes deposited on 5 MHz quartz plates. Solid-supported lipid bilayers were composed of an initial octanethiol monolayer chemisorbed on gold and a physisorbed phospholipid monolayer varying in its lipid composition as the outermost layer. The integrity of bilayer preparation was monitored by impedance spectroscopy. For binding experiments, a protein construct comprising the RafRBD and Raf-C1 linked to the maltose binding protein and a His tag, termed MBP-Raf-C1, wa…
In situ synthesis of lipopeptides as versatile receptors for the specific binding of nanoparticles and liposomes to solid-supported membranes.
2008
A detailed study of the in situ coupling of small peptides such as CGGH6 (H6) and CGWK8 (K8) to maleimide functionalized phospholipid bilayers is presented. Individually addressable microstructured membranes are employed to unequivocally probe the conjugation. The in situ coupling of peptides via a terminal cysteine moiety to maleimide functionalized phospholipids is shown to be a convenient and versatile way to selectively fabricate peptide-modified phospholipid bilayers serving as specific receptor platforms for functionalized vesicles and nanoparticles. Specific binding of functional vesicles to the peptide-modified bilayers is achieved by either histidine complexation with Ni-NTA-DOGS c…
Reaction of melatonin with lipoperoxyl radicals in phospholipid bilayers.
1997
Melatonin, at 5 to 500 microM was incorporated in unilamellar soybean phosphatidylcholine (PC) liposomes, the peroxidation of which was induced by 2,2'-azobis (2-amidinopropane-hydrochloride) (AAPH), and measured as production of conjugated diene lipid hydroperoxides. Concentration as low as 5 and 10 microM were poorly effective in reducing lipid peroxidation. Melatonin at 30 to 500 microM caused short inhibition periods, increasing with, but not linearly related to concentration, with a concurrent net decrease of the propagation rate. The time course of melatonin oxidation, measured as loss of fluorescence, was studied during the AAPH-stimulated peroxidation of soybean PC liposomes, or whe…
Interaction of Quinine with Model Lipid Membranes of Different Compositions
2002
The binding of a drug such as Quinine with neutral and negatively charged small unilamellar lipid vesicles at pH 7 and 37 degrees C was investigated. Changes in the fluorescence properties of the drug after association with the liposomes were used to obtain binding isotherms over a range of phospholipid compositions at different ionic strengths. Under such conditions, the association was strongly enhanced by the negative net charge of the bilayer but diminished by the increasing presence of electrolytes in the aqueous media. Binding data were analyzed in terms of a surface partition equilibrium without and after correcting for electrostatic effects by means of the Gouy-Chapman theory. The i…
The impact of humic and fulvic acids on the dynamic properties of liposome membranes: the ESR method
2013
This paper presents the results of research on the influence of two fractions of humic substances (HS): fulvic acids (FA) and humic acids (HA), as a function of concentration, on the liposome membranes formed from egg yolk lecithin (EYL). The concentration of HS in relation to EYL changed from 0% to 10% by weight. The influence of HS on various areas of membranes: interphase water-lipid, in the lipid layer just below the polar part of the membrane and in the middle of the lipid bilayer, was investigated by different spin labels (TEMPO, DOXYL 5, DOXYL 16). The study showed that HA slightly decreased the fluidity of the analyzed membranes on the surface layer, while FA significantly liquidate…
Electrically induced deformation of giant liposomes monitored by thickness shear mode resonators.
2006
Thickness shear mode resonators are capable of registering small changes in the thickness and viscoelastic properties of ultrathin films attached to their surface. It was found that it is possible to monitor the deformation of surface-bound giant liposomes by applying an electric field with small amplitudes. Changes in the apparent height of attached vesicles in the nanometer range were easily detected as a function of lipid composition. Increasing the bending modulus by adding cholesterol results in a significantly reduced deformation from 16.8 nm (5% cholesterol) down to 3.2 nm (20% cholesterol), rendering this new method a robust and sensitive tool to detect the bending elasticity of lip…