1. Laboratory for Biological and Medical Mass Spectrometry, Uppsala University, Box 583 Biomedical Centre, SE-75123 Uppsala, Sweden, Department of Pharmaceutical Biosciences, Uppsala University, Biomedical Centre, SE-75123 Uppsala, Sweden, Department of Biochemistry and Mass Spectrometry Research Center, Vanderbilt University School of Medicine, 465 21 Avenue South, Nashville, Tennessee 37232-8575, USA, and Department of Physiology and Pharmacology, Karolinska Institutet, SE-17177 Stockholm, Sweden