[1] IAC Mauro Picone (CNR), Viale del Polidinico 137, 00161 Rome, Italy
[2] Department of Theoretical Biophysics, Humboldt University, Invalidenstrasse 42, D-10115 Berlin, Germany
[3] Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115
[4] Department of Cell Biology, Harvard Medical School, Boston, MA