Division for Simulation of Biological Systems, Center for Bioinformatics, Eberhard-Karls University, 72076 Tübingen, Germany. npfeifer@informatik.uni-tuebingen.de|Division for Simulation of Biological Systems, Center for Bioinformatics, Eberhard-Karls University, 72076 Tübingen, Germany. npfeifer@informatik.uni-tuebingen.de|Division for Simulation of Biological Systems, Center for Bioinformatics, Eberhard-Karls University, 72076 Tübingen, Germany. npfeifer@informatik.uni-tuebingen.de|Division for Simulation of Biological Systems, Center for Bioinformatics, Eberhard-Karls University, 72076 Tübingen, Germany. npfeifer@informatik.uni-tuebingen.de