1. Biomolecular Mass Spectrometry Laboratory, Swiss Federal Institute of Technology in Lausanne, Lausanne, CH-1015, Switzerland, Ion Cyclotron Resonance Program, National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310-4005, and Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306