Physico-chemical framework of the amino acids in the proteomes of Archaea, Bacteria, and Eukaryota. (a) The 20 amino acids were classified into hydrophobic, charged, and polar and uncharged amino acids based on the polarity of their side chains. (b) The 20 amino acids were classified into aliphatic, aromatic, and heterocyclic amino acids based on the chemical structure of their side chains. The related data processing methods were as described in the legend to Figure 1.
Chen et al. BMC Evolutionary Biology 2013 13:219 doi:10.1186/1471-2148-13-219