1. Drug Research Program and Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, P.O. Box 56, Helsinki 00014, Finland
2. Viikki Metabolomics Unit, Faculty of Biological and Environmental Sciences, University of Helsinki, P.O. Box 56, Helsinki 00014, Finland
3. Department of Environmental and Biological Sciences, Institute of Photonics, Faculty of Science and Forestry, University of Eastern Finland, P.O. Box 111, Joensuu 80101, Finland