Figure 3.

(a) Fluorescence absorption and emission spectra before (red line) and after (blue line) photoactivation, along with the fluorescence emission spectrum (green solid line). Arrowhead indicates region of maximum absorbance in active state, with no absorbance before photoactivation. Absorbance values of activated protein (blue) correspond to the excitation spectrum for fluorescence. (b) Time series of photoactivation for HbGFP with two different excitation sources: magenta dashed line, 15.0 mW at 450 nm; blue solid line, 0.3 mW at 460 nm. (c) Time series of fluorescence decay. Solid line shows the data, whereas dashed grey line is an overlay of the fitted exponential decay function. Note that time scales on (b) and (c) are different.