<p>(a) -codes for the SCOP protein dataset reveal at a glance several geometric properties of the set. Each column represents a histogram of the indicated protein class, normalized so that the largest value is unity. A feature common to all classes is the prominence of <i>α</i>-helices ( ≈0.36). Another common feature is the presence of loops that connect ordered secondary structure ( ≈0.62). Moreover, <i>α</i>-helical regions are prominently visible in ‘all-<i>β</i>’ proteins. (b) The -code for a peptoid nanosheet shows two dominant rotational states, which coexist within a single secondary structure (see Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160023#pone.0160023.g005" target="_blank">5</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160023#pone.0160023.g007" target="_blank">7</a>).</p
