4XTQ:
reference: Molecular Basis of Spectral Diversity in Near-Infrared Phytochrome-Based Fluorescent Proteins., Shcherbakova DM, Baloban M, Pletnev S, Malashkevich VN, Xiao H, Dauter Z, Verkhusha VV, Chem Biol. 2015 Nov 19;22(11):1540-51. doi: 10.1016/j.chembiol.2015.10.007. PMID: 26590639

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