Search results for "layer"

Quadratic Nonlinear Behaviour of Various Langmuir-Blodgett Molecules

1989

The Langmuir-Blodgett (L-B) technique is well known as a method of building-up ordered arrays of organic molecules, and especially as a means of imposing a noncentrosymmetric structure from molecules that crystallize in a centrosymmetric space group(1–3). L-B films for use in quadratic nonlinear optics can be ordered in a statistically noncentrosymmetric lattice. The method involves the compression of a mono-layer of the organic molecule, spread on top of a water surface, into a two-dimensional solid, followed by the repeated dipping of the substrate to be coated into and out of the subphase. Monolayers may be deposited onto the substrate both on immersion and withdrawal, resulting in a cen…

Structural properties of phosphatidylcholine in a monolayer at the air/water interface

1991

Neutron reflectivities of phosphatidylcholine monolayers in the liquid condensed (LC) phase on ultrapure H 2 O and D 2 O subphases have been measured on a Langmuir film balance. Using a dedicated liquid surface reflectometer, reflectivities down to R = 10 -6 in the momentum transfer range Q z = 0–0.4A -1 were accessed. In a new approach, by refining neutron reflectivity data from chain-perdeuterated DPPC-d 62 in combination with x-ray measurements on the same monolayer under similar conditions it is shown that the two techniques mutually complement one another. This analysis leads to a detailed conception of the interface structure. It is found that in the LC phase (which is analogous to th…

Phase diagrams of monolayers of the long chain fatty acids

1990

Micelles, monolayers and biomembranes. By M. N. Jones, D. Chapman, Wiley-Liss, New York 1995, XII, 252 pp., hardcover $69.00, ISBN 0-471-56139-8

1996

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

1993

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)…

The Phase Behaviour of Amphiphilic Monolayers

1991

Amphiphilic monolayers display a wealth of condensed phases. It is only recently that these have been widely recognised as being distinct, but they are in fact quite analogous to the well-known lamellar gel phases of bulk lyotropic and thermotropic mesogens. An understanding of these phases has proved to be important for controlling the defect structure of the monolayers used in the fabrication of Langmuir-Blodgett films. This understanding is being achieved by developments in a number of techniques, including X-ray diffraction and isotherm miscibility. The phase diagrams of the materials studied so far are all very closely related, lending new credibility to the principle of corresponding …

Monolayer phases of the fatty acids and their ethyl esters

1991

The miscibility correspondence between water-surface monolayer phases of the fatty acids and their ethyl esters was determined. Ester phases were found corresponding to all the known phases of the acids, and vice versa, in similar relative positions of the π-T diagram. Evidence is presented for the existence of a ninth distinct miscibility category, represented by a phase in each of the pure materials, and a tenth found only in mixtures. We propose a tentative correspondence to bulk smectic miscibility categories.

DOMAIN AND MOLECULAR SUPERLATTICE STRUCTURE OF DODECANETHIOL SELF-ASSEMBLED ON AU(111)

1994

Annealed organic monolayers of dodecanethiol (CH3(CH2)11SH) self-assembled on Au(111) have been investigated by scanning tunnelling microscopy. By using very high tunnelling resistances (TOMEGA) we find evidence of well-ordered molecular domains at room temperature and observe two different types of c(4 x 2) superlattice structures with the same rectangular unit cell. In contrast to theoretical calculations each unit cell contains four inequivalent molecules. Possible reasons for this discrepancy are discussed.

Poly[bis(μ-pentafluorobenzenethiolato)lead(II)]

2006

The title compound, [Pb(SC6F5)2]n, exhibits a layered structure containing two differently hexa­coordinated PbII atoms. One is situated on a centre of inversion and is coordinated by six S atoms, its valence lone pair of electrons being consequently stereochemically inactive. The other Pb atom is pyramidally coordinated by three S atoms and forms three contacts to adjacent F atoms, the stereochemically active lone pair pointing towards the F3 plane.

Structure Of Complexes Of Helix-5 From Bax With Lipid Membranes

2009

Bax is a proapoptotic protein implicated in the release of cell-death activating factors from the mitochondrial intermembrane space. Although the structure of the membrane-bound forms of Bax is unknown, it has been proposed to form proteolipidic pores. Studies with synthetic lipid vesicles have shown that fragments encompassing helix-5 of Bax retain a membrane permeabilization ability that is similar to that of the full-length protein. Here we report on the structure of peptide-membrane complexes formed by a Bax helix-5 peptide and lipid bilayers. The relative orientation of the peptide and the lipids are determined using site-specific infrared spectroscopy, assisted by isotopic labeling of…