Amino acid properties affected by positive selection. Amino acid properties affected by positive-destabilizing (A) and positive-stabilizing (B) selection. Pc, coil tendencies; F, mean r.m.s. fluctuation displacement; Et, total non-bonded energy; P
, α-helical tendencies; pK', equilibrium constant. The z-scores (Y axis) correspond to the proportion of observed amino acid replacements per magnitude category (X axis) . The dashed lines indicate the critical z-scores limits. The significant categories are marked with an asterisk.