Fig. 2: Mutation scan, charge separation, and subsequent reactions.
From: Dynamics and mechanism of dimer dissociation of photoreceptor UVR8
a Steady-state emission spectra (λpu = 290 nm) of WT and all 15 mutants are shown in different colors. Three groups of mutants: with both W285 and W233, without W233, and without W285. Their emission peaks are ~332 nm, ~336 nm, and ~354 nm, respectively (dotted lines). b Fluorescence decay transients of WT and four mutants at 315-nm excitation. The fitting results are also shown. Note the critical 80-ps quenching component only in the presence of both W285 and W233. The delay time is shown on a linear scale before 300 ps and a logarithmic scale thereafter. c Broadband transient absorption spectra of WT (blue lines), W285/233F (orange lines), and indole/CCl4 model system (gray lines) at various delay times at 290-nm excitation. For shape comparison, absolute intensities of the spectra were adjusted by multiplying by different factors, as labeled near the left side of each spectrum. The spectral difference due to Trp cation radicals (W+•) was shaded by light green color. d Broadband transient absorption spectra of WT (blue lines), W285F (red lines) at various delay times at 315-nm excitation. For shape comparison, absolute intensities of the spectra were adjusted by multiplying by certain factors, as labeled near the left side of each spectrum. The spectral difference due to Trp cation radicals (W+•) and by Trp neutral radicals was shaded in light green and light blue colors, respectively. e The transient dynamics of WT and W285F probed at 630 nm upon 315-nm excitation. For WT, the transient was deconvoluted into two components of Trp excited state W* (dark yellow dashed line) and Trp cation radical W+• (green dashed line). The symbols are experimental data and the lines are best fit. The first 48-ps data are shown in the inset. The W+• signal and its components of W233+•W285 (dark red dash-dot line) and W233+•W285-• (cyan dash-dot line) were multiplied by 10 for clarity. Note the initial ~3.2-ps rise in WT. f Reaction mechanism and time scales. CS-charge separation between W285 and W233; ET-electron transfer from W285−• to positive R286+/R338+; CR-charge recombination of W285−• and W233+•; DP-deprotonation of W233+• to D129. Time scales for each reaction step are shown. The charge recombination (CR) step is a futile branching.
