Condensed phases in monolayers of a triple-chain lecithin on water

Abstract A triple-chain phospholipid monolayer at the air-water interface is investigated by means of grazing incidence X-ray diffraction (GID). Analysis of the diffraction spot profiles parallel and perpendicular to the surface yields different ordered phases. On increasing the lateral pressure at different temperatures the hydrocarbon chains form tilted phases with a tilt toward the nearest neighbors and eventually a hexagonal lattice with vertical chain orientation.

Domain shapes and monolayer structures of triple-chain phospholipids on water

Two triple-chain phospholipid isomers were investigated at the air-water interface by means of fluorescence microscopy and grazing incidence X-ray diffraction (GID). The two lipids differ only in the position of the branched chain at the glycerol backbone. Fluorescence microscopy shows different domain sharp-edged domains. In the case of dendritic domains the chains are more tilted, the deviation from hexagonal symmetry is more pronounced and hence the lattice anisotropy is larger.

Ex-voto anatomiques en bois : catalogue et commentaires xylologiques comparés des sites de Magny-Cours (Bourgogne) et de Nesle, Mesnil-Sainte-Nicaise (Picardie)

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Morphology and structures in double-, triple- and quadruple-chain phospholipid monolayers at the air/water interface

The structure of double-, triple- and quadruple-chain phospholipid monolayers has been studied by Synchrotron x-ray diffraction. The double-chain mixed- linkage species exhibit an oblique structure at all pressures investigated. The triple-chain phospholipids show at lower lateral pressures a rectangular unit cell with a phase transition at higher pressures to a hexagonal packing of vertically arranged chains. The quadruple- chain lipid exhibits only the hexagonal phase structure. The position of the ether linkage and of the branched chain on the glycerol backbone has also a strong influence on the monolayer structures. Fluorescence microscopy shows different domain shapes for the different…

Domain formation in monolayers

For phospholipids at the air/water interface we demonstrate that molecular chirality in some, but not in all, cases influences the domain shapes. In other cases chirality in the head group region can cause a chiral structure considering the tail arrangement. This indicates head group ordering. Minute changes of the molecular structure may change domain morphology from circular to dendritic. This can be related to slight changes of the lattice structure. In case of a dendritic domain the chains are more tilted, the deviation from hexagonal symmetry is more pronounced, and hence the lattice anisotropy is larger. This can be understood also in view of recent simulations considering diffusion-l…

LAB-STEM CELLS

Polymorphic domains in monolayers of isomeric triple-chain phospholipids

Monolayers of two isomeric branched chain phosphatidyl cholines at the air/water interface have been studied by means of fluorescence microscopy. The lipids differ in the position of the branched chain at the glycerol backbone and carry three chains per headgroup of almost equal length. Most qualitative features of the compression isotherms are similar except a difference of 4 A2/molecule in the minimum molecular area at high lateral pressures. This indicates a more condensed solid phase of compound C2 and is also reflected in the shapes of domains observed in the LE/LC phase coexistence range: domains with sharp edges and a mostly hexagonal shape are formed. On the other hand, the compound…