1. Department of Physical Biochemistry, Max Planck Institute for Biophysical Chemistry, 37077 Goettingen, Germany.
2. Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, 37077 Goettingen, Germany.
3. Bioanalytics, Department of Clinical Chemistry, University Medical Center Goettingen, 37075 Goettingen, Germany.