Red
fluorescent proteins with a large Stokes shift offer a limited
autofluorescence background and are used in deep tissue imaging. Here,
by introducing the free amino group in Aequorea victoria, the electrostatic charges of the p-hydroxybenzylidene
imidazolinone chromophore of green fluorescent protein (GFP) have
been altered resulting in an unusual, 85 nm red-shifted fluorescence.
The structural and biophysical analysis suggested that the red shift
is due to positional shift occupancy of Glu222 and Arg96, resulting
in extended conjugation and a relaxed chromophore. Femtosecond transient
absorption spectra exhibited that the excited state relaxation dynamics
of red-shifted GFP (rGFP) (τ4 = 234 ps) are faster
compared to the A. victoria green fluorescent
protein (τ4 = 3.0 ns). The nanosecond time-resolved
emission spectra of rGFP reveal the continuous spectral shift during
emission by a solvent reorientation in the chromophore. Finally, the molecular dynamics simulations
revealed the rearrangement of the hydrogen bond interactions in the
chromophore vicinity, reshaping the symmetric distribution of van
der Waals space to fine tune the GFP structure resulting from highly
red-shifted rGFP.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.