1. Bioinformatics Group, Institute of Computer Science, Interdisciplinary Center of Bioinformatics , Leipzig University , Härtelstraße 16-18 , D-04107 Leipzig , Germany
2. Max-Planck-Institute for Mathematics in the Sciences , Inselstraße 22 , D-04103 Leipzig, Germany
3. Institute of Theoretical Chemistry, University of Vienna , Währingerstraße 17 , A-1090 Wien , Austria
4. Facultad de Ciencias , Universidad National de Colombia , Sede Bogotá , Colombia
5. Santa Fe Institute , 1399 Hyde Park Rd. , Santa Fe , NM 87501 , USA