Fig. 3. (a) Fluorescence emission spectra of d-luciferin (1) (green line), infra-luciferin (4) (red line) and 5 (black line). Dotted lines are normalized spectra, (b) pH dependence of fluorescence spectra of d-luciferin (1) (330 nm excitation), (c) infra-luciferin (4) (352 nm excitation), and (d) 5 (369 nm excitation) measured in 5 nm increments.
