Rational design of genetically encoded singlet oxygen photosensitizing proteins.

Reactive oxygen species (ROS), such as the superoxide anion, the hydroxyl radical and singlet oxygen, can influence cellular processes in many ways. However, the molecular mechanisms of ROS action in cells are still poorly understood. As such, we need to develop tools that can better elucidate ROS behavior in the dynamic environment of a cell. Optogenetics provides one approach to this end. Using a genetically encoded protein-encased photosensitizer, one could produce a given ROS with a controllable yield in a specific intracellular domain or compartment. A palette of ROS sensitizing protein derivatives has emerged and, in this review, we use information gleaned from recent studies to discuss properties that define a 'good' singlet oxygen photosensitizing protein.