Distributions of the torsion angles α, γ, δ, and ζ for the single RNA (first row) and the collection of RNAs (second row). We observe the similitude among the distributions, marking the presence of “rotamers” not only for a given RNA but also across RNAs. We also observe clear modes, which are automatically detected by the proposed clustering technique. In addition, note that the ζ torsion angle has a large tail not present in the other distributions.