1. Institute of Chemistry, University of Campinas (UNICAMP), Campinas, SP 13083-970, Brazil
2. Univ Lyon, Université Claude Bernard Lyon 1, INSERM, Stem Cell and Brain Research Institute U1208, 69500 Bron, France
3. Laboratoire Léon Brillouin, UMR12, Bat 563 CEA Saclay, 91191 Gif sur Yvette Cedex, France