Structural and Genomic Information, CNRS-UPR 2589, 31 chemin Joseph Aiguier, 13009 Marseille, France. enault@igs.cnrs-mrs.fr|Structural and Genomic Information, CNRS-UPR 2589, 31 chemin Joseph Aiguier, 13009 Marseille, France. enault@igs.cnrs-mrs.fr|Structural and Genomic Information, CNRS-UPR 2589, 31 chemin Joseph Aiguier, 13009 Marseille, France. enault@igs.cnrs-mrs.fr