Phototoxicity of halogenofluorescein derivatives in Dictyostelium discoideumamoebae: comparison of 2',4',5',7'-tetrabromofluorescein- and 4',5'-diiodofluorescein dextran

The characteristics of 2',4',5',7'-tetrabromoflourescein is discussed in terms of its usefulness as anefficient photosensitizer in the selection of new mutants of endocytosis. I2FD and Br4FD could both produce singlet oxygen as shown by their abilities to mediate bleaching of p-nitrosoaniline in the presence of histidine. Intracellular uptake of Br4FD showed that it could be used as a fluid phase marker in D. amoebae. Br4FD was three times more efficient than I2FD in terms of photosensitizer effectivity.