C. Seebacher et al., Stable low-temperature photoproducts and hole burning of green fluorescentprotein (GFP), J PHYS CH B, 103(36), 1999, pp. 7728-7732
We present low-temperature optical investigations down to 2 K of the photoc
hemistry and hole burning of wild-type green fluorescent protein (wt-GFP).
Three new photoproducts with absorption at 489, 502, and 510 nm (P489, P502
, P510, respectively) are identified by fluorescence excitation and fluores
cence spectroscopy. The data suggest that P502 is identical with the obliga
tory intermediate of the excited-state deprotonation cycle R-neq(-) that ex
ists only as a transient at room temperature. The second new product P510 i
s also associated with R-neq(-), whereas P489 is related to the equilibrate
d anionic form R-eq(-). An extended energy scheme accounting for these new
species is presented. The ground-state energy barriers characterizing these
products have been determined by temperature-dependent studies. Low-temper
ature persistent spectral hole burning in the red wing of the R-eq(-) absor
ption has been demonstrated and can be used to characterize electron-phonon
coupling.