[Fluorescent photobleaching of endogenous protoporphyrin IX in yeast cells]

Yeast Saccharomyces cerevisiae accumulate in the presence of chelator 2,2'-dipyridyl, two fractions of photosensitizer protoporphyrin IX, which fluoresce with maxima at 625 and 635 nm. The two fractions were found to differ from each other in the dynamics and character of fluorescence photobleaching. In contrast to the protoporphyrin IX that fluoresces with a maximum at 625 nm, the protoporphyrin IX fraction that fluoresces with a maximum at 635 nm is more photolable; in addition, upon photobleaching of its fluorescence, a new maximum at 675 nm appears.