Department of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany. ruping@molgen.mpg.de|Department of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany. ruping@molgen.mpg.de|Department of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany. ruping@molgen.mpg.de|Department of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany. ruping@molgen.mpg.de|Department of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany. ruping@molgen.mpg.de|Department of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany. ruping@molgen.mpg.de|Department of Computational Molecular Biology, Max-Planck-Institute for Molecular Genetics, Ihnestr. 63-73, 14195 Berlin, Germany. ruping@molgen.mpg.de