Caged compounds, the photolabile precursors of bioactive molecules. Developments and prospects

Caged compounds have been developed to allow a rapid and efficient photolytic release of a biomolecule within organized biological systems. This methodology permits more accurate time-resolved measurements, mainly because it overpasses effector's diffusion problems. Among the different photochemical protecting groups which have been described, the ortho-nitrobenzyl group is the most widely used caging group, allowing the photochemical protection of several chemical functions. The subsequent photolytic release of the biomolecules is usually fast and efficient but suffers from the formation of deleterious side products. para-Hydroxyphenacyl and coumarin derivatives represent more potent protecting groups for the caging of biomolecules. A series of applications using caged compounds, including protein folding, dynamic crystallography and two-photons photolysis, are described.