6APP:
reference: Unveiling a Drift Resistant Cryptotope within Marburgvirus Nucleoprotein Recognized by Llama Single-Domain Antibodies., Garza JA, Taylor AB, Sherwood LJ, Hart PJ, Hayhurst A, Front Immunol. 2017 Oct 2;8:1234. doi: 10.3389/fimmu.2017.01234. eCollection, 2017. PMID: 29038656

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