Search results for "Lipids"
showing 10 items of 2228 documents
Local control of antibody binding to hapten-presenting interfaces: Steric and electrostatic interaction
1991
The binding of labeled antibodies to hapten substituted monolayers at the air/water interface has been studied by means of fluorescence microscopy. Haptens with various spacer lengths between the epitope and a hydrocarbon chain, anchoring the molecule to the interface, have been synthesized. With DMPC,a unspecific binding has been shown to predominate over specific binding due to electrostatic interactions. At high surface pressures the bound antibody is detached because of steric interference with the lipid head groups. Due to a reduction of electrostatic interactions, no unspecific binding is observed to monolayers of cholesterol, which carries a small dipole moment. Mixed monolayers of c…
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…
Comparison of linear and hyperbranched polyether lipids for liposome shielding by 18F-radiolabeling and positron emission tomography
2018
Multifunctional and highly biocompatible polyether structures play a key role in shielding liposomes from degradation in the bloodstream, providing also multiple functional groups for further attachment of targeting moieties. In this work hyperbranched polyglycerol (hbPG) bearing lipids with long alkyl chain anchor are evaluated with respect to steric stabilization of liposomes. The branched polyether lipids possess a hydrophobic bis(hexadecyl)glycerol membrane anchor for the liposomal membrane. hbPG was chosen as a multifunctional alternative to PEG, enabling the eventual linkage of multiple targeting vectors. Different hbPG lipids (Mn = 2900 and 5200 g mol-1) were examined. A linear bis(h…
Sterol Composition in Infant Formulas and Estimated Intake.
2015
Sterol contents in infant formulas (IFs) from the European market were determined, and their intakes by infants between 0 and 6 months were evaluated. Total animal sterols (mg/100 mL) ranged from 1.71 to 5.46, cholesterol being the main animal sterol (1.46-5.1). In general, cholesterol and desmosterol were lower than the human milk (HM) values indicated by other authors. Total plant sterol (mg/100 mL) ranged from 3.1 to 5.0. β-Sitosterol, the most abundant phytosterol, ranged from 1.82 to 3.01, followed by campesterol (0.72-1.15), stigmasterol (0.27-0.53), and brassicasterol (0.14-0.28). Cholesterol intake (mg/day) ranged from 9 to 51 and plant sterol intake (mg/day) from 19 to 50. The ster…
Interaction between biotin lipids and streptavidin in monolayers: formation of oriented two-dimensional protein domains induced by surface recognitio…
1989
Highly specific ligand-receptor interactions generally characterize surface recognition reactions. Such processes can be simulated by streptavidin-biotin-specific binding. Biotin lipids have thus been synthesized, and their interaction with streptavidin (or avidin) at the air-water interface was directly shown by measurement of surface pressure isotherms and fluorescence microscopy. These proteins interact with the biotin lipid monolayer via specific binding or nonspecific adsorption. Both phenomena were clearly distinguished by use of the inactivated form of streptavidin. The binding of fluorescein-labeled streptavidin to monolayers was also directly observed by fluorescence microscopy. Th…
X-ray diffraction of a protein crystal anchored at the air/water interface
1995
We report the first successful in situ x-ray diffraction experiment with a 2D protein array at the lipid/water interface and demonstrate that the order can be controlled via lateral pressure or density. A protein (streptavidin) was bound to a monolayer of biotinylated lipid at the air/water interface, and diffraction of the protein layer could be measured to many orders. Compression of the monolayer changed the diffraction pattern drastically, indicating that the protein structure can be strongly influenced by external parameters like lateral pressure or density. From the width of the peaks, we find that aggregates consisting of as few as 100 monomers contribute to the diffraction. This ind…
Formation of protein multilayers and their competitive replacement based on self-assembled biotinylated phospholipids.
1994
Based on specific recognition processes the build-up of protein multilayers was achieved using streptavidin layers as a docking matrix. For this purpose, streptavidin was organized at biotin-containing monolayers, liposomes, and self-assembled layers on gold. Thus, mixed double and triple layers of streptavidin, Con A, Fab fragments, and hormones were prepared and characterized by fluorescence microscopy and plasmon spectroscopy. Using biotin analogues with lower binding constants several cycles of multilayer formation followed by competitive replacement could be achieved.
Molecular recognition in biotin-streptavidin systems and analogues at the air-water interface
1992
Abstract Specific interaction between biotin and the protein streptavidin in monolayers of synthetic lipids with biotin headgroups has been shown to lead to formation of highly ordered two-dimensional streptavidin crystals. The same behaviour is observed when using desthiobiotin as lipid headgroup which exhibits a significantly lower binding constant compared with biotin (5 × 10 13 M -1 compared with 10 15 M -1 ). This offers the possibility of detaching competetively the 2D crystalline streptavidin layer by addition of free biotin to the aqueous phase. Use of lipoic acid as lipid headgroup ( K a = 7 × 10 7 M −1 ) leads to formation of small snisotropic protein domains indicating a crystall…
Influence of surface chemistry on the structural organization of monomolecular protein layers adsorbed to functionalized aqueous interfaces.
1993
The molecular organization of streptavidin (SA) bound to aqueous surface monolayers of biotin-functionalized lipids and binary lipid mixtures has been investigated with neutron reflectivity and electron and fluorescence microscopy. The substitution of deuterons (2H) for protons (1H), both in subphase water molecules and in the alkyl chains of the lipid surface monolayer, was utilized to determine the interface structure on the molecular length scale. In all cases studied, the protein forms monomolecular layers underneath the interface with thickness values of approximately 40 A. A systematic dependence of the structural properties of such self-assembled SA monolayers on the surface chemistr…
Functionalized lipid tubules as tools for helical crystallization of proteins
1997
The development of functional supramolecular devices built by self-assembly of elementary molecules and with bioactive properties arouses considerable interest in the field of nanotechnology and new materials. We report here the formation of a new class of lipid tubules exhibiting both properties of molecular recognition and crystal formation for the protein streptavidin. These lipid tubules, made of biotin-containing dioctadecylamine molecules, are straight hollow cylinders with a constant diameter of 27 nm and variable length up to several micrometers. They are unilamellar with an inner diameter of about 16 nm, as shown by cryoelectron microscopy. Streptavidin binds to the biotinylated tu…