1. Department of Biology, Institute of Molecular Systems Biology, and
2. Competence Center for Systems Physiology and Metabolic Diseases, ETH Zurich, CH 8093, Switzerland;,
3. Biomolecular Mass Spectrometry and Proteomics, University of Utrecht, and Netherlands Proteomics Center, 3584 CH Utrecht, The Netherlands;
4. Faculty of Science, University of Zurich, CH 8006 Switzerland