Center for Biological Sequence Analysis--CBS, Department of Systems Biology, The Technical University of Denmark--DTU, Kemitorvet Build. 208, 2800 Lyngby, Denmark. lunde@cbs.dtu.dk|Center for Biological Sequence Analysis--CBS, Department of Systems Biology, The Technical University of Denmark--DTU, Kemitorvet Build. 208, 2800 Lyngby, Denmark. lunde@cbs.dtu.dk|Center for Biological Sequence Analysis--CBS, Department of Systems Biology, The Technical University of Denmark--DTU, Kemitorvet Build. 208, 2800 Lyngby, Denmark. lunde@cbs.dtu.dk