Center for Biological Sequence Analysis, Technical University of Denmark, Building 208, DK-2800 Lyngby, Denmark. rodrigo@cbs.dtu.dk|Center for Biological Sequence Analysis, Technical University of Denmark, Building 208, DK-2800 Lyngby, Denmark. rodrigo@cbs.dtu.dk|Center for Biological Sequence Analysis, Technical University of Denmark, Building 208, DK-2800 Lyngby, Denmark. rodrigo@cbs.dtu.dk