Monolayer and bilayer systems applied to the study of the stability, structural dynamics and microheterogeneity of biomembranes

RAFAEL GUSTAVO OLIVEIRA

Buenos Aires

Taller; Humboldt Colloquium ?Shaping the Future of German-Argentinian Scientific Cooperation ? The Role of Curiosity-Driven Research?; 2018

Alexander von Humboldt Foundation

We work on biophysical aspects related to the structure of biomembranes, mainly based on the model myelin membrane. The main focuses are on: a) the phase coexistence over the lateral plane in the very same monolayer and b) the interaction between adjacent layers. Regarding the first point, the response of such phase separation to different environmental variables (temperature, solutes) is studied, as well as changes in the monolayer composition and molecular packing, determining interfacial tensions (surface and line tensions), electrostatic repulsion and points of mixing. The final goal is to produce phase diagrams for these systems. These studies started up by using monolayers at the air/water interface and on solid supports, on which we perform fluorescence microscopy and Brewster angle microscopy. Currently, we continue such studies in monolayers improving the techniques to quantitative Brewster angle microscopy (reflectivity, refractive index and subnanometric thickness) and grazing incidence x-ray scattering techniques (at the National Laboratory of Synchrotron Light, Campinas Brazil) in order to obtain diffraction and diffuse scattering patterns, which tell us about the structural organization of the monomolecular films. These approaches were learnt at ESRF. Concomitantly, we extend the models beyond the monolayer to bilayers or multilayers in order to tackle the second objective of our plan, about the interaction between layers. For these new systems, we are carrying out also structural determinations using small angle X-ray scattering (SAXS) as well as wide angle x-ray scattering (WAXS) at the National Laboratory of Synchrotron Light (LNLS), Campinas Brazil; we started this tradition at Hasylab, DESY. Also we perform neutron diffraction (at the Institute Laue Langevin, Grenoble, France, starting from the AvH fellow), among others with the goal of establishing possible correspondences in the phase diagram of the monolayer and bilayer systems. Currently we collaborate as users in order to establish these techniques at LAHN, Argentina. Additionally, we help to set up new grazing incidence techniques at LNLS which will be fully operative in the new synchrotron SIRIUS, Campinas. The scattering techniques in their different variations found its natural applications (beyond the biomembrane realm) in other nano-structured material and interfacial systems.