1. Department of Biochemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
2. Department of Physics, Trento University, Via Sommarive 14, 38123 Povo (Trento), Italy
3. SISSA, Via Bonomea 265, 34136 Trieste, Italy
4. INFN-TIFPA, Via Sommarive 14, 38123 Povo (Trento), Italy
5. Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland