6V21:
reference: Sub-2 Angstrom resolution structure determination using single-particle cryo-EM at 200keV., Wu M, Lander GC, Herzik MA Jr, J Struct Biol X. 2020 Feb 28;4:100020. doi: 10.1016/j.yjsbx.2020.100020., eCollection 2020. PMID: 32647824

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