5GV8:
reference: Distribution of valence electrons of the flavin cofactor in NADH-cytochrome b5 reductase., Takaba K, Takeda K, Kosugi M, Tamada T, Miki K, Sci Rep. 2017 Feb 22;7:43162. doi: 10.1038/srep43162. PMID: 28225078

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