3DMK:
reference: A double S shape provides the structural basis for the extraordinary binding specificity of Dscam isoforms., Sawaya MR, Wojtowicz WM, Andre I, Qian B, Wu W, Baker D, Eisenberg D, Zipursky SL, Cell. 2008 Sep 19;134(6):1007-18. PMID: 18805093

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