| 5VBS: reference: Structure and Biophysics for a Six Letter DNA Alphabet that Includes Imidazo[1,2-a]-1,3,5-triazine-2(8H)-4(3H)-dione (X) and 2,4-Diaminopyrimidine (K)., Singh I, Kim MJ, Molt RW, Hoshika S, Benner SA, Georgiadis MM, ACS Synth Biol. 2017 Nov 17;6(11):2118-2129. doi: 10.1021/acssynbio.7b00150. Epub, 2017 Aug 15. PMID: 28752992 |
This OCA 
Structure page
uses Jmol,
developed by the Jmol Development Team
(documentation).