Average electrostatic free energy of folding as a function of the number of electrostatic mutations.

<p>Each point on a curve corresponds to , where is the number of sequences with electrostatic mutations, is the probability of the th sequence under a given model conditional upon the number of mutations, and is its electrostatic folding energy (<a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1002675#pcbi.1002675.e068" target="_blank">Equation (1)</a>; see Methods). All points are plotted relative to , the average of observed sequences with one electrostatic mutation. The black curve shows the average energies of observed sequences , the red curve represents the average energies of sequences under a model in which each charge state occurs with equal frequency, the blue curve shows the average energies of sequences under a model in which each charge state occurs with frequencies observed in the data, and the green curve represents the average energy of sequences under a pair correlation model which preserves observed pair frequencies. The error bars on the black curve are the standard errors of the mean of observed sequences. Note that for .