1 Institute of Chemistry and Biology of Membranes and Nano-objects, CNRS, U. of Bordeaux, Bât. B14, allée Geoffroy St. Hilaire, 33600 Pessac, France. Electronic address: i.alves@cbmn.u-bordeaux.fr.
2 Laboratoire Ondes et Matière d'Aquitaine, CNRS, U. of Bordeaux, Bât. A4N, 351 cours de la libération, 33405 Talence, France. Electronic address: christine.grauby-heywang@u-bordeaux.fr.