1. Department of Microbiology and Immunology; Center for Single Molecule Biophysics, University at Buffalo; Buffalo New York
2. Departament de Física Fonamental; Facultat de Física, Universitat de Barcelona, Diagonal 647, 08028; Barcelona Spain
3. CIBER-BBN de Bioingenieria, Biomateriales y Nanomedicina, Instituto de Sanidad Carlos III; Madrid Spain