The significance of the above comments is as follows. Of the amino acids with charged sidechains, only aspartate (D) and histidine (H) appear to favor such binding in the present author's analysis, while glutamate (E) arginine (R), lysine (K) have zero valued parameters and so are contraindications of sialic acid or sialic acid glycan binding. However, the latter three charged amino acid residue can sometimes be found in scialic acid binding sites and in sites predicted as such by the present method. Indeed, they are often dominant features of residues directly interacting with sialic acid. In the sialic acid binding site of the globular head region of the Newcastle disease virus haemagluttinin a glutamate (E), three arginine residues (R) and a lysine (K) are intimate contact with sialic acid ligand. A difference is that these residues make intimate contact in space and are not together in a one or very few subsequences. That is, they do not necessarily constitute a sequence motif.