Grazing-incidence X-ray scattering studies of myelin membranes at air/water interface

Full text: Thin and ultrathin films in liquid surfaces and interfaces have been intensively studied in different domains such as pharmaceutics, electronics, and food industry. These materials represent a model case to study the dynamical and structural properties of 2D confined soft matter. A very interesting class of ultrathin films is given by the Langmuir monolayers, which are monomolecular layers of amphiphilic molecules spread on air/water interfaces, since they can represent a model for biological systems. Langmuir monolayers formed by myelin lipids or full myelin membranes offer advantageous features to approach the exploration of the surface properties of a complex lipid-protein interface since they contain all the components of natural membranes[1]. Surface-sensitive synchrotron-based X-ray scattering techniques such as grazing-incidence diffraction (GID) and scattering (GISAXS/GIXOS) are powerful tools for investigating the molecular structure of organic films on liquid surfaces due to the penetrating properties of the X-rays and the ability to couple structural and dynamical properties of interfaces with nanoscale resolution[2]. We present in this work the first results of a surface-sensitive X-ray scattering experiment performed at LNLS/XRD-2 beamline[3]. We used this technique to study Langmuir monolayers formed by myelin lipids and full myelin membranes as a function of the monolayer surface pressure. The new experiment opens new possibilities for the soft condensed matter community in Brazil. The structural study as a function of the change of preparation conditions and thermodynamical parameters make this kind of experiment ideal for many technological and industrial applications. A. (author)