Search results for "bilayers"

Calorimetric Behavior of Phosphatidylcholine/Phosphatidylethanolamine Bilayers is Compatible with the Superlattice Model

2012

Differential scanning calorimetry was used to study the phase behavior of binary lipid bilayers consisting of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of varying acyl chain length. A two-state transition model was used to resolve the individual transition components, and the two-state transition enthalpy, the relative enthalpy, and the transition temperature of each component were plotted as a function of composition. Intriguingly, abrupt changes in these thermodynamic parameters were observed at or close to many "critical" X(PE) values predicted by the superlattice model proposing that phospholipids with different headgroups tend to adopt regular rather than random latera…

Functional competition within a membrane: Lipid recognition vs. transmembrane helix oligomerization

2015

Abstract Binding of specific lipids to large, polytopic membrane proteins is well described, and it is clear that such lipids are crucial for protein stability and activity. In contrast, binding of defined lipid species to individual transmembrane helices and regulation of transmembrane helix monomer–oligomer equilibria by binding of distinct lipids is a concept, which has emerged only lately. Lipids bind to single-span membrane proteins, both in the juxta-membrane region as well as in the hydrophobic membrane core. While some interactions counteract transmembrane helix oligomerization, in other cases lipid binding appears to enhance oligomerization. As reversible oligomerization is involve…

Cluster organization and pore structure of ion channels formed by beticolin 3, a nonpeptidic fungal toxin

1999

Beticolin 3 (B3) belongs to a family of nonpeptidic phytotoxins produced by the fungus Cercospora beticola, which present a broad spectrum of cytotoxic effects. We report here that, at cytotoxic concentration (10 microM), B3 formed voltage-independent, weakly selective ion channels with multiple conductance levels in planar lipid bilayers. In symmetrical standard solutions, conductance values of the first levels were, respectively, 16 +/- 1 pS, 32 +/- 2 pS, and 57 +/- 2 pS (n = 4) and so on, any conductance level being roughly twice the lower one. Whether a cluster organization of elementary channels or different channel structures underlies this particular property was addressed by investi…

Formation of irreversibly bound annexin A1 protein domains on POPC/POPS solid supported membranes

2008

AbstractThe specific interaction of annexin A1 with phospholipid bilayers is scrutinized by means of scanning force and fluorescence microscopy, quartz crystal microbalance, ellipsometry, and modeled by dynamic Monte Carlo simulations. It was found that POPC/POPS bilayers exhibit phase separation in POPC- and POPS-enriched domains as a function of Ca2+ concentration. Annexin A1 interacts with POPC/POPS bilayers by forming irreversibly bound protein domains with monolayer thickness on POPS-enriched nanodomains, while the attachment of proteins to the POPC-enriched regions is fully reversible. A thorough kinetic analysis of the process reveals that both, the binding constant of annexin A1 at …

Phospholipid and phospholipid-protein monolayers at the air/water interface.

1990

Force Measurements on Myelin Basic Protein Adsorbed to Mica and Lipid Bilayer Surfaces Done with the Atomic Force Microscope

1999

The mechanical and adhesion properties of myelin basic protein (MBP) are important for its function, namely the compaction of the myelin sheath. To get more information about these properties we used atomic force microscopy to study tip-sample interaction of mica and mixed dioleoylphosphatidylserine (DOPS) (20%)/egg phosphatidylcholine (EPC) (80%) lipid bilayer surfaces in the absence and presence of bovine MBP. On mica or DOPS/EPC bilayers a short-range repulsive force (decay length 1.0-1.3 nm) was observed during the approach. The presence of MBP always led to an attractive force between tip and sample. When retracting the tip again, force curves on mica and on lipid layers were different…

No Label Required: Protein Binding at Membrane Interfaces Visualized through Colloid Phase Transitions

2004

Phase Transition of Individually Addressable Microstructured Membranes Visualized by Imaging Ellipsometry

2007

The phase transition of individually addressable microstructured lipid bilayers was investigated by means of imaging ellipsometry. Microstructured bilayers were created on silicon substrates by micromolding in capillaries, and the thermotropic behavior of various saturated diacyl phosphatidylcholine (1,2-dipalmitoyl-sn-glycero-3-phosphocholine, 1,2-dipentadecoyl-sn-glycero-3-phosphocholine, and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)) bilayers as well as DMPC/cholesterol membranes was determined by measuring the area expansion and thickness of the bilayer as a function of temperature. We found an increase in the main phase transition temperature T(M) of 2-6 degrees C and a substa…

Thermal Expansion of Microstructured DMPC Bilayers Quantified by Temperature-Controlled Atomic Force Microscopy

2006

Unusual triskelion patterns and dye-labelled GUVs: consequences of the interaction of cholesterol-containing linear-hyperbranched block copolymers wi…

2015

Cholesterol (Ch) linked to a linear-hyperbranched block copolymer composed of poly(ethylene glycol) (PEG) and poly(glycerol) (hbPG) was investigated for its membrane anchoring properties. Two polyether-based linear-hyperbranched block copolymers with and without a covalently attached rhodamine fluorescence label (Rho) were employed (Ch-PEG30-b-hbPG23 and Ch-PEG30-b-hbPG17-Rho). Compression isotherms of co-spread 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) or 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with the respective polymers were measured on the Langmuir trough and the morphology development of the liquid-condensed (LC) domains was studied by epi-fluorescence microsc…