The crystal structures of both the historic 1918 NA as well as the avian flu NA are available in complex with currently used drugs. We created a homology model of the new 2009 swine flu NA to map the sequence differences to the three-dimensional structure templates. Using Modeller [32] , the sequence of the new neuraminidase [Genbank Accession: ACP41107.1 http://www.ncbi.nlm.nih.gov/ protein/227809834] was modelled 50 times onto multiple templates (PDB: 2hu4 [33] , 3ckz [34] , 3b7e [35] , 3beq [35] ) and the resulting best model (as judged by DOPE score) further refined with short simulated annealing MD simulations in the presence of a bound inhibitor (zanamivir, oseltamivir or peramivir) as implemented in the Yasara Structure package [36] . The final atom-resolution models are available in PDB format at http://men del.bii.a-star.edu.sg/SEQUENCES/H1N1/.