ASAXS measurements on ferritin and apoferritin at the bioSAXS beamline P12 (PETRA III, DESY).

Small-angle X-ray scattering is widely utilized to study biological macromol-ecules in solution. For samples containing specific (e.g. metal) atoms, additional information can be obtained using anomalous scattering. Here, measuring samples at different energies close to the absorption edges of relevant elements provides specific structural details. However, anomalous small-angle X-ray scattering (ASAXS) applications to dilute macromolecular solutions are challenging owing to the overall low anomalous scattering effect. Here, pilot ASAXS experiments from dilute solutions of ferritin and cobalt-loaded apoferritin are reported. These samples were investigated near the resonance X-ray K edges of Fe and Co, respectively, at the EMBL P12 bioSAXS beamline at PETRA III, DESY. Thanks to the high brilliance of the P12 beamline, ASAXS experiments are feasible on dilute protein solutions, allowing one to extract the Fe- or Co-specific anomalous dispersion terms from the ASAXS data. The data were subsequently used to determine the spatial distribution of either iron or cobalt atoms incorporated into the ferritin/apoferritin protein cages.

A THz transparent 3D printed microfluidic cell for small angle x-ray scattering.

Excitation frequencies in the terahertz (THz) range are expected to lead to functionally relevant domain movements within the biological macromolecules such as proteins. The possibility of examining such movements in an aqueous environment is particularly valuable since here proteins are not deprived of any motional degrees of freedom. Small angle x-ray scattering (SAXS) is a powerful method to study the structure and domain movements of proteins in solution. Here, we present a microfluidic cell for SAXS experiments, which is also transparent for THz radiation. Specifically, cell dimensions and material were optimized for both radiation sources. In addition, the polystyrene cell can be 3D printed and easily assembled. We demonstrate the practicality of our design for SAXS measurements on several proteins in solution.

Short periodicity phase based on ceramide [AP] in the model lipid membranes of stratum corneum does not change during hydration.

Small angle X-ray scattering technique was used to determine electron density profiles of short periodicity phase in the model lipid membranes of stratum corneum at different pH. Basic quaternary system was prepared as used previously in the neutron experiments at partial hydration. It was shown that electron density profiles of partially hydrated and fully hydrated model lipid membranes with four basic components were quite similar and demonstrated almost no interbilayer water.

Application of small-angle X-ray scattering to the characterization and quantification of the drug transport nanosystem based on the soybean phosphatidylcholine.

Phospholipid transport nanosystem (PTNS) for drug delivery is based on soybean phosphatidylcholine. The morphology of PTNS is investigated by means of small-angle X-ray scattering. The obtained results allow one to answer the key question from the viewpoint of organization of drug incorporation whether the PTNS nanoparticles have a structure of micelles or vesicles. It is demonstrated that PTNS is a vesicular system with an average vesicle radius of 160 ± 2Å.

Fuzzy cold dark matter: the wave properties of ultralight particles.

Cold dark matter (CDM) models predict small-scale structure in excess of observations of the cores and abundance of dwarf galaxies. These problems might be solved, and the virtues of CDM models retained, even without postulating ad hoc dark matter particle or field interactions, if the dark matter is composed of ultralight scalar particles (m approximately 10(-22) eV), initially in a (cold) Bose-Einstein condensate, similar to axion dark matter models. The wave properties of the dark matter stabilize gravitational collapse, providing halo cores and sharply suppressing small-scale linear power.

Strongly Polarized Optical Afterglows of Gamma-Ray Bursts.

The optical afterglows of the gamma-ray bursts can be strongly polarized, in principle up to tens of percents, if (1) the afterglow is synchrotron radiation from an ultrarelativistic blast, (2) the blast is beamed during the afterglow phase, i.e., the shock propagates within a narrow jet, (3) we observe at the right time from the right viewing angle, and (4) magnetic fields parallel and perpendicular to the jet have different proper strengths.