1. Peptide and Protein Group, European Molecular Biology Laboratory (EMBL), 69012 Heidelberg, Germany, Structural and Computational Biology Program, European Molecular Biology Laboratory (EMBL), 69012 Heidelberg, Germany, MDS Sciex, 71 Four Valley Drive, Concord ON L4K 4V8, Canada, and Department of Physics and Astronomy, University of Manitoba, Winnipeg MB R3T 2N2, Canada