Figure 4.

A) Surface representation of the structural model of the neuraminidase domain of the new strain in complex with zanamivir. Coloring is based on sequence conservation over all NA subtypes. Grey means no conservation. Other colors are according to physical properties: yellow ... hydrophobic, green ... polar, blue ... positive charge, red ... negative charge. Color intensities are proportional to strength of conservation. B) Mapping of new mutations to structure. Cyan colored residues are mutations at typical antibody recognition sites. Blue residues indicate differences to both the H5N1 avian flu as well as H1N1 from the 1918 Spanish flu. Yellow residues are intra-strain variations occurring in multiple patients of the 2009 H1N1 outbreak and orange if they have only been found in isolated patients, so far. Note that the intra-strain variation N248D is colored cyan since it is part of the antibody recognition site. The backbone of the antibody recognition sites is colored green and the bound drug and 3 calcium ions are shown in red.