Spectral Versatility of Fluorescent Proteins Observed on the Single Molecule Level - Fluorescent Proteins: From Understanding to Design - page 226

DsRed

DsRed2

Fluorescent
Timer

DsRed
N42H

AG4

500 600 700 500 600 700 500 600 700

λ /nm λ /nm λ /nm

Fig. 9 Single tetramer spectra of DsRed and the analyzed variants. For all proteins emission
spectra showing solely green emission ( first column ), mixed emission ( second column ), or solely
red emission ( third column ) were found. The emission from the red-emitting chromophore was
systematically shifted to the red, consistent with the fast formation of a super-red form. The
frequencies of occurrence of the respective spectra were consistent with the bulk spectra, displayed
in grey behind the predominantly observed spectrum (From [ 88 ], Copyright Wiley-VCH Verlag
GmbH & Co. KGaA. Reproduced with permission)

Indeed, all variants for which the super-red form was found contain a glutamate
residue at position 215; thus, the universal observation of the super-red form
is consistent with this proposed mechanism. However, the super-red form was