Fig. 2.

Intra-type, site-specific amino acid residue entropy. Residue variation estimated using Shannon entropy, wherein a value of zero reflects site-specific conservation and higher values indicate increasing degrees of site-specific variation. A level of 5% residue variation equates to an entropy score of ca. 0.18. Site-specific variation(s) above this level are indicated by convention, numbered according to the reference sequence for that HPV type. The positions of major structural elements are indicated.