1PEN:
reference: The 1.1 A crystal structure of the neuronal acetylcholine receptor antagonist, alpha-conotoxin PnIA from Conus pennaceus., Hu SH, Gehrmann J, Guddat LW, Alewood PF, Craik DJ, Martin JL, Structure 1996 Apr 15;4(4):417-23. PMID: 8740364

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