New tools for the structural characterization of membrane systems

OLIVEIRA, RAFAEL GUSTAVO

La Plata

Encuentro; XLVII Reunión Anual de la Sociedad Argentina de Biofísica; 2018

Sociedad Argentina de Biofísica

New emerging techniques are allowing the experimental determination of structural parameters in membrane systems at the South Cone. The first one is a complementation of classical reflectivity in a Brewster angle microscope (BAM). By contrast matching we experimentally determine the refractive index of Langmuir monolayers. The refractive index and reflectivity allow us to calculate the thickness of the films as a function of surface pressure. In order to evaluate what kind of thickness is actually measured, the results from BAM were compared to the ones determined by GIXOS (Grazing Incidence X-ray Off Specular Scattering). The last is a new setup that substitutes the specular X-ray reflectivity on the determination of the perpendicular structure of the monolayer. This setup is currently working at the Brazilian Synchrotron, rendering the first results which will be more meaningful at the future synchrotron Sirius. The comparison of GIXOS and BAM thicknesses, among other measurements in bilayers and multilayers, (SAXS and XRD) allows us to determine that the BAM setup measures the whole thickness of the monolayer. Additionally, the grazing incidence setup is allows measuring the first X-ray diffractions at wide angle. At Sirius, with an X-ray beam 104 more powerful, the new data at grazing incidence will be obtained faster, allowing kinetic acquisition and full modeling of the data over extended scattering vector range. For the next step, we are considering to couple the grazing incidence setup to an X-ray fluorescence detector over the monolayer; this will allow mapping of the vertical distribution of the heavier elements from Z=15. Finally, the Laboratorio Argentino de Haces de Neutrones (LAHN) is planning for the second round of instrumentation a Neutron Reflectometer and a Small Angle Neutron Scattering instrument. Altogether, these efforts will cover different systems from monolayer to bi- and multi-layers in a set of variable environmental conditions. CONCTRIBUCION NO DICTADA POR ACCIDENTE FAMILIAR.