X-ray spectral diagnostics of the local environment of zinc in the arachidic acid layers

The article describes the behaviour of the Zn ions in aqueous subphase in presence of arachidic acid films at the air/liquid interface first studied by XANES spectroscopy in the fluorescent mode under total external reflection conditions. Fingerprint analysis of experimental spectra was carried out to determine the local structure of zinc ions in arachidic acid. It showed that zinc is surrounded by oxygen atoms, which may correspond to the interaction of zinc ions with polar groups of arachidic acid.

Impact of polyphenol-rich green tea extracts on the protection of DOPC monolayer against damage caused by ozone induced lipid oxidation

Effectiveness of green tea (compared to two single polyphenols) in removing ozone derived reactive oxygen species acting on dioleoyl phosphatidylcholine monolayers was determined. The lipid oxidation was followed by changes of mechanical properties of the layer spreaded on the aqueous subphase containing various amounts of ozone in presence and absence of polyphenolics. It was shown that tea extract (containing 8.5x10-4 mg/cm3 polyphenols) is capable of inactivating 0.4 ppm ozone.The DPPH radical scavenging test set polyphenols in the order of increasing activity, consistent with their protective effect in relation to lipid oxidation, showing the highest efficacy of EGCG.

Structure of a monolayer of molecular rotors on aqueous subphase from grazing-incidence X-ray diffraction

In situ grazing-incidence X-ray scattering shows that a monolayer of artificial rod-shaped dipolar molecular rotors produced on the surface of an aqueous subphase in a Langmuir trough has a structure conducive to a 2D ferroelectric phase. The axes of the rotors stand an average of 0.83 nm apart in a triangular grid, perpendicular to the surface within experimental error. They carry 2,3-dichlorophenylene rotators near rod centers, between two decks of interlocked triptycenes installed axially on the rotor axle. The analysis is based first on simultaneous fitting of observed Bragg rods and second on fitting the reflectivity curve with only three adjustable parameters and the calculated rotor electron density, which also revealed the presence of about seven molecules of water near each rotator. Dependent on preparation conditions, a minor and variable amount of a different crystal phase may also be present in the monolayer.

PROTEIN MONOLAYER FORMATION AT AIR–ELECTROLYTE INTERFACE: A LANGMUIR–BLODGETT STUDY

The interfacial surface activity of a protein, ovalbumin (OVA) at bare air/water interface in presence and also in absence of electrolyte (KCl) in subphase has been investigated. The surface activity was measured as a function of time. It has been found that, the presence of KCl in aqueous subphase enhances the adsorption rate of the protein. The changes of area/molecule, compressibility, rigidity and unfolding of OVA are trivial up to 10 mM KCl concentration. These properties of OVA, above 10 mM KCl concentration are significant and have been explained in the perspective of DLVO theory and many-body ion–protein dispersion potentials. The presence of high concentration of electrolyte increases the β-structure of OVA, resulting into larger unfolding as well as larger intermolecular aggregates. The overall study indicates that KCl perturbs the OVA monolayer.