Figure 6. Fluorescence excitation spectra of human insulin (emission fixed at 303 nm) upon prolonged 276 nm UV-excitation.

The excitation spectra (em. 303 nm) were obtained before and after 276 nm light continuous exc. (0.5 h, 1 h, 1.5 h, 2.5 h, 3.5 h, and 7 h) of human insulin in solution. There is a continuous decrease in excitation intensity at 276 nm with 276 nm exc. time.