Effect of entropies of 0 on MI scores. The percent of columns in an MSA that have an entropy of 0 is plotted against the percent of all domain-domain residue pairs in the corresponding complex that have an MI value of 0. Only those columns in the MSA that correspond to a residue in the reference structure are used. Columns that have one or more gaps are ignored. Each point on the plot represents a single case study in our domain-domain dataset.