values averaged over the methods (left y-axis scale) and the average RMSD of the reference alignments for each superfamily. The Fcar(0) (filled circle) and Fcar(8) (open circle) values (scale on the left y-axis) of each superfamily are connected by a vertical grey line. Average RMSDs are shown by inverse triangles with error bars on the negative side only (scale on the right y-axis). Two superfamilies with exceptionally high RMSD are marked in red. The structures in these superfamilies (one of the split cd00365 and cd00172) contain sub-structures that are flexibly joined to the rest of the structure. The inset shows the distribution of average Fcar(0) with bin size of 0.05 in semi-logarithmic scale. The dots represent the observed frequencies and the line is best fitting exponential curve to the observed frequencies.