Influence of chirality on the structure of phospholipid monolayers.

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.

Behenic Acid as a Structural Model for Fatty Acid Monolayers at the Air/Water Interface: An X-Ray Diffraction Study

We present an X-ray diffraction study of behenic (docosanoic) acid films at the air/water interface. Analysis of the rod profiles parallel and perpendicular to the surface provides detailed information on the unit cells of five different phases.

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…

X-ray scattering studies of fatty acid films on water and on Cdcl2 solutions

X-ray diffraction methods for Langmuir films on the surface of water are briefly presented, together with recent results for docosanoic acid monolayers on pure water and for eicosanoic acid monolayers on an ionic subphase.

Electron Diffraction and Imaging of Uncompressed Monolayers of Amphiphilic Molecules on Vitreous and Hexagonal Ice

A new approach is described for probing domains of ordered self-assemblies of amphiphilic monolayers at the aqueous solution interface. The method has potential importance for the study of membrane structure, Langmuir-Blodgett films, and nucleation processes of two-and three-dimensional crystals. Electron diffraction (ED) patterns indicative of two-dimensional crystalline self-assembly were obtained from samples, which were examined by cryo-electron microscopy, of monolayers of water-insoluble amphiphiles on vitrified aqueour substrates. The apparent hexagonal symmetry of an ED pattern from a C(16)H(33)OH monolayer was interpreted in terms of multiple twinning. Monolayers of the CL(31)H(63)…

X-Ray Scattering Studies of Organic Monolayers on Electrolytic Solutions: Arachidic Acid on CdCl2

The interaction between a charged monolayer of fatty acid molecules on the surface of a CdCl2 aqueous solution and the ions below has been investigated by means of X-ray Reflection and Grazing-Incidence Diffraction. A stoichiometric, localised layer of Cd++ ions forms an epitaxial 2×3 superstructure below the 2D-crystalline fatty acid monolayer.