1ZHU:
reference: Structure of a single-cytidine hairpin loop formed by the DNA triplet GCA., Zhu L, Chou SH, Xu J, Reid BR, Nat Struct Biol 1995 Nov;2(11):1012-7. PMID: 7583654

This OCA Structure page
uses Jmol, developed by the Jmol Development Team (documentation).