Excerpts

The fluorescence of asFP595 is extremely weak (quantum yield , 0.001); nevertheless, the purple protein can be detected by spectrofluorimetry (Fig. 3B). When viewed by fluorescence microscopy, the novel protein shows an unexpected feature; although the fluorescence at 595 nm is virtually imperceptible at the start of observation, the emission intensity increases dramatically following a 10 –20-s exposure to green light (Fig. 4B). This effect is reversible because in the absence of incident green light, the fluorescence capacity slowly decreases to the basal level. Even more surprisingly, asFP595 fluorescence can be quenched by a flash of blue light (Fig. 4C). This effect strongly depends on intensity of irradiation: the brighter the light the more pronounced increasing and quenching of the fluorescence.