1. Department of Chemistry, University of Bergen, Bergen 5020, Norway
2. Computational Biology Unit, Department of Informatics, University of Bergen, Bergen 5020, Norway
3. European Molecular Biology Laboratory, EMBL, Meyerhofstrasse 1, Heidelberg D-69117, Germany
4. Department of Cell Physiology and Metabolism, University of Geneva, CMU Rue Michel-Servet 1, Genève 4 1211, Switzerland