Quantitative determination of element distributions in biomembrane models at the air/water interface by grazing-incidence X-ray fluorescence

AHMED DÍAZ PÁEZ; GALVÁN JOSA, VICTOR M.; FERNÁNDEZ BORDÍN SANTIAGO P; PUSTERLA JULIO MARTÍN; DUPUY FERNANDO G; OLIVEIRA, RAFAEL GUSTAVO

Campinas

Encuentro; 28 REUNIÃO ANUAL DE USUÁRIOS; 2018

Brazilian Material Research Society

In the Annual User´s Meeting of 2012 we proposed to install a Grazing incidence setup for Langmuir monolayers at the air/water interface; this means in horizontal sample geometry (Oliveira, 22 RAU). Such setup evolved [1] and is currently producing the very first published works [2]. This setup will be translated to SIRIUS at the SAGUI beamline where the performance will increase significantly (Antonio Gasperini, personal communication). Moreover, the time consuming and sometimes difficult experiments will be performed much quick and easier due to the higher photon flux, allowing getting GIXOS and GIXD on second time scales. Then, performing additional measurements on the same monolayer can be affordable and desirable. In this opportunity, we propose to couple the existing grazing incidence setup of the Langmuir trough with a fluorescence detector. By slights modifications of the incident grazing angle (with the very same system to deflect the beam below the critical angle for total reflection in grazing incidence setup), the penetration length of the evanescent wave will be modified. This allows the differential excitation of X-ray fluorescence of atoms present along the vertical profile of the monolayer itself or in the counter-ion layers beneath it. This will help during the electron density modelling of the monolayer itself and/or to account for the distribution of ionic layers [3]. Of course, this setup will be useful in other biomembrane model systems like solid supported layers.References[1] Vieira CEP, Gasperini AM, Freitas PPS, Oliveira RG, Cavalcanti LP. J. Synchrotron Rad. 22, 859-861 (2015)[2] Pusterla JM, Gasperini-Malfatti AM, Puentes-Martinez X, Cavalcanti LP, Oliveira RG. BBA Biomembr. 1859:924-930.[3] Schneck E, Schubert Th, Konovalov OV, Quinn BE, Gutsmann T, Brandenburg K, Oliveira RG, Pink DA, Tanaka M. PNAS 107: 9147-9151 (2010)