6DQ0:
reference: Crystal structures of green fluorescent protein with the unnatural amino acid 4-nitro-L-phenylalanine., Maurici N, Savidge N, Lee BU, Brewer SH, Phillips-Piro CM, Acta Crystallogr F Struct Biol Commun. 2018 Oct 1;74(Pt 10):650-655. doi:, 10.1107/S2053230X1801169X. Epub 2018 Sep 19. PMID: 30279317

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