Principal components analysis of amino acids in the proteomes of species from the three domains. The distribution of points on the principal factorial planes is shown. One point corresponds to one species. (a) Projections onto a 3D principal plane spanned by the principal component 1 (Prin1), Prin2, and Prin3 axes. (b–d) Projections onto the three 2D factorial planes in the Prin1, Prin2, and Prin3 axes, respectively.
Chen et al. BMC Evolutionary Biology 2013 13:219 doi:10.1186/1471-2148-13-219