1. Contribution from the Department of Biomolecular Mass Spectrometry, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, The Netherlands, Department of Biochemistry and Molecular Biology, Faculty of Sciences, Vrije Universiteit, Amsterdam, The Netherlands, Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, United Kingdom, and FOM Institute for Atomic and Molecular Physics (AMOLF), The Netherlands