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. 2004 Dec 21;88(3):1932–1947. doi: 10.1529/biophysj.104.044412

FIGURE 4.

FIGURE 4

Excited-state proton transfer efficiences and quantum yields derived from the spectral data. (a) ESPT efficiencies in the GFP variants. The asterisk denotes the variants with strong blue RH fluorescence, which prevents an accurate determination of the ESPT quantum yield. Low quantum yield values might be caused by an unavoidable blue-edge excitation of the deprotonated form, by a subconformation with fast ESPT in the S65G/E222-variants like in EGFP (Cotlet et al., 2001), or by an alternative ESPT-mechanism (McAnaney et al., 2002; Winkler et al. 2002). The large error bars in a result from the weak absorbance of the neutral form or from the strong overlap of the RH and R− fluorescence emissions. (b) Fluorescence quantum yields ΦFl for the neutral form referenced to the deprotonated form in wt-GFP with ΦFl = 0.8. The large error bars in b result from weak absorbance of the neutral form. (c) Fluorescence quantum yields for the deprotonated form referenced to wt-GFP with ΦFl = 0.8. The values obtained by the Strickler-Berg relation are indicated by hatched bars (Strickler and Berg, 1962).