Figure 1. Amino acid interaction energies and occurrence frequencies.

(Left A) Natural occurrence frequency of amino acids in complete proteome sets averaged over a wide variety of prokaryotes obtained from UniParc database (for a complete list see Supporting Table Information 1). Error bars denote one standard deviation fluctuations. The frequencies are well-conserved from species to species. (Right B) MJ matrix: inter-residue contact-energies between any two types of amino acids in units of k_BT, computed by Miyazawa and Jernigan³⁰.