Subcellular, Time-resolved Studies of Singlet Oxygen in Single Cells

In time-resolved and spatially resolved experiments, singlet molecular oxygen, O2(a1Deltag), was created in a single nerve cell upon irradiation of a sensitizer incorporated in the cell using a focused laser beam. The singlet oxygen thus produced was detected by its infrared phosphorescence. Data obtained indicate that in both the cytoplasm and the nucleus of the cell, this reactive species is approximately 1-2 orders of magnitude longer-lived than previously believed. The data demonstrate that deactivation of singlet oxygen in the cell is dominated by interactions with the solvent not cellular constituents such as proteins. These results provide a new perspective for mechanistic studies of the role of O2(a1Deltag) in photoinduced cell death and intracellular signaling.