Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, D-04107 Leipzig, Germany.|Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, D-04107 Leipzig, Germany.|Center for Anatomy and Cell Biology, Medical University of Vienna, Austria.|Institute for Biochemistry, Leipzig University, D-04103 Leipzig, Germany.|Bioinformatics Group, Department of Computer Science, and Interdisciplinary Center for Bioinformatics, D-04107 Leipzig, Germany.|Department of Theoretical Chemistry of the University of Vienna, A-1090 Vienna, Austria.