Anomalous photophysical behaviors attributed to coherent coupling in evolutionarily divergent fluorescent protein dimers

LanYFP, avGFP, and dsRED are fluorescent proteins (FPs) isolated from marine organisms which diverged in pre-Cambrian oceans over 541 million years ago. While they have < 30% sequence homology, and their spectra, absorption coefficients, and quantum yields differ, they do share a common 𝛽-barrel protein structure. Here we show that despite divergent evolution tandem dimers (TDs) derived from these FPs all show 4 anomalous photophysical behaviors consistent with exciton formation and super-radiant emission. Our findings indicate that divergent FPs can couple coherently under physiological conditions and suggest that their conserved 𝛽-barrel structure is the common attribute supporting exciton formation and super-radiant emission under physiological conditions.