1. Biomolecular Mass Spectrometry Laboratory, Ecole Polytechnique Fédérale de Lausanne, CH-1015, Lausanne, Switzerland
2. Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida, USA
3. Ion Physics Laboratory, State Polytechnical University, St. Petersburg, Russia
4. Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, USA