Search results for "INTERFACE"
showing 10 items of 2139 documents
Chemically driven phase separation in black lipid membranes and its coupling to membrane functions
1992
Abstract We analysed the single-channel current fluctuations of gramicidin in bimolecular lipid membranes in order to demonstrate (i) the influence of protein binding to the lateral organisation of a mixed membrane, and (ii) how this couples to the function of the ionophore. Examples of phase separations induced by synthetic polyelectrolytes, as models for peripheral membrane proteins, and specific ligand-receptor interactions are presented and discussed in view of the important lateral order-function relationship in biomembranes.
Oxo-Vanadium(IV) Dihydrogen Phosphate: Preparation, Magnetic Study, and Heterogeneous Catalytic Epoxidation
2008
A layered oxo-vanadium(IV) dihydrogen phosphate, {VO(H2PO 4)2} n has been synthesized hydrothermally and characterized by several physicochemical methods. Single-crystal X-ray analysis (crystal system, tetragonal; space group, P4/ ncc; unit cell dimensions, a = b = 8.9632(4), c = 7.9768(32) A) of {VO(H2PO4) 2} n reveals that the compound has an extended two-dimensional structure. The VO2+ moieties are connected through bridging H 2PO4 (-) ions, and this type of connection propagates parallel to the crystallographic ab plane which gives rise to a layered structure. The layers are staked parallel to the crystallographic c axis with a separation between the layers of ca. 4.0 A. Magnetic suscep…
Molecular topology applied to the discovery of 1-benzyl-2-(3-fluorophenyl)-4-hydroxy-3-(3-phenylpropanoyl)-2H-pyrrole-5-one as a non-ligand-binding-p…
2014
We report the discovery of 1-benzyl-2-(3- fluorophenyl)-4-hydroxy-3-(3-phenylpropanoyl)-2H-pyrrole- 5-one as a novel non-ligand binding pocket (non-LBP) antagonist of the androgen receptor (AR) through the application of molecular topology techniques. This compound, validated through time-resolved fluorescence resonance energy transfer and fluorescence polarization biological assays, provides the basis for lead optimization and structure−activity relationship analysis of a new series of non-LBP AR antagonists. Induced-fit docking and molecular dynamics studies have been performed to establish a consistent hypothesis for the interaction of the new active molecule on the AR surface. Refereed/…
Studies of Molecular Orientation and Order in Self-Assembled Semifluorinated n-Alkanethiols: Single and Dual Component Mixtures
1997
The structure, orientation and morphology of self-assembled monolayers of a semifluorinated n-alkanethiol, F(CF2)8(CH2)11SH (F8H11SH), have been investigated by polarized IR, angular dependent XPS, ToF-SIMS, contact angle, and ellipsometric measurements. The orientation of the all trans hydrocarbon segment was found to be tilted much less from the surface normal than the 30° tilt found for octadecanethiol. This has been attributed to the steric constraints imposed by the larger cross section fluorocarbon helices that subsequently are tilted from the surface normal. In addition, studies of dual component mixtures of F8H11SH/F8SH and F8SH/F8H2SH have revealed that competitive adsorption occur…
Tuning the Self-Assembly of Rectangular Amphiphilic Cruciforms
2014
The self-assembly of a series of nonionic amphiphilic cruciforms based on the 1,2,4,5-tetrakis(phenylethynyl)benzene (TPEB) skeleton, in which the peripheral substituents have been modified to modulate the morphology of the supramolecular structures, is reported. The presence of linear paraffinic and hydrophilic chains in TPEBs 1 and 2 gives rise to two-dimensional structures of high aspect ratio. In contrast, the incorporation of dendronized hydrophilic chains results in the formation of twisted ribbons in amphiphile 3 and impedes the organized self-assembly of TPEB 4. Theoretical calculations show that the self-assembly of these amphiphiles might be initiated with the formation of π-stack…
Molecular Recognition via Hydrogen Bonding at the Air−Water Interface: An Isotherm and Fourier Transform Infrared Reflection Spectroscopy Study
1997
Molecular recognition in Langmuir monolayers at the air−water interface as a function of headgroup orientation and substrate using isotherms and in-situ Fourier transform infrared (FT-IR) reflection spectroscopy has been investigated. Isotherm measurements show that urea and 2,4,6-triaminopyrimidine (TAP) are specifically bound to barbituric acid lipid monolayers. As expected, TAP causes a larger shift in the limiting area of the isotherms than urea due to steric requirements. The peak positions of the CH stretching vibrations of the barbituric acid lipids indicate that the alkyl chains of barbituric acid lipids 1−3 are in a close-packed all-trans conformation both before and after the reco…
A spatially resolved investigation of oxygen adsorption on polycrystalline copper and titanium by means of photoemission electron microscopy
2004
Abstract The interaction of oxygen with polycrystalline copper and titanium surfaces was studied by means of photoemission electron microscopy. Variations in the image brightness were used to determine the work function of different Cu crystallites. The change of the work function was monitored during oxygen adsorption on both, Cu and Ti. Those changes are smooth for Cu whereas different Ti crystallites exhibit a rather complicated behavior during oxygen adsorption. The transformation of brightness versus exposure curves into work function versus coverage curves allows to determine the initial dipole moment of the adsorbed oxygen atoms. A value of about 20 mD was found for O on Cu(1 1 0). V…
Specific recognition and formation of two- dimensional streptavidin domains in monolayers: applications to molecular devices
1989
Abstract By virtue of the high-affinity specific interaction between the vitamin, biotin, and the protein, streptavidin, monolayers of synthetic lipids with biotin headgroups can tightly bind streptavidin at the lipid-water interface. Through this specific recognition fluorescently-labelled streptavidin spontaneously organizes in the plane of the interface to form large protein domains, directly visible in situ by fluorescence microscopy and exhibiting optical anisotropy. Further structural characterization has shown that these domains are two-dimensional protein crystals. Correlation with the known three-dimensional crystal structure of streptavidin indicates that two of streptavidin's fou…
Pressure dependent arrangement of a protein in two-dimensional crystals specifically bound to a monolayer
1993
Abstract The arrangement of streptavidin bound to a biotinylated monolayer of a polymeric amphiphile at the air-water interface is studied as a function of lateral pressure or ligand density. Closely packed domains are observed by fluorescence microscopy. The arrangement of the protein in these domains is sensitively detected by X-ray reflectivity and an especially thorough data analysis yields the following: the distance of the protein from the air-monolayer interface varies with lateral pressure by 10 A; the interfaces involving the protein are much rougher than expected due to capillary waves; the electron density of the protein layer increases considerably on compression, which can be u…
Molecular recognition processes at functionalized lipid surfaces: a neutron reflectivity study
1992
The specific binding of proteins to functionalized monolayers on aqueous subphases has been characterized by neutron reflectivity measurements. As a model for the investigation of a recognition process on a molecular length scale, streptavidin (SA) and biotin were chosen because of the high specific affinity between them. Reflectivities from the aqueous (NaCl/H2O or NaCl/D2O) surfaces covered with the biotin-lipid monolayers before and after the adsorption of proteins were collected with a novel, fixed wavelength liquid surface neutron reflectometer. In quantitative terms, binding was found to occur at a biotin surface concentration as low as 1 molecule/1250 A2 (compare to ∼ 1 molecule/40 A…