2N2K:
reference: Lys63-linked ubiquitin chain adopts multiple conformational states for specific target recognition., Liu Z, Gong Z, Jiang WX, Yang J, Zhu WK, Guo DC, Zhang WP, Liu ML, Tang C, Elife. 2015 Jun 19;4. doi: 10.7554/eLife.05767. PMID: 26090905

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