A caged protein is a protein that is activated in the presence of a stimulating light source. In most cases, photo-uncaging is the technique revealing the active region of a compound by the process of photolysis of the shielding molecule (‘cage’). However, uncaging the protein requires an appropriate wavelength, intensity, and timing of the light. Achieving this is possible due to the fact that the optical fiber may be modified to deliver specific amounts of light. In addition, short bursts of stimulation allow results similar to the physiological norm. The steps of photostimulation are time independent in that protein delivery and light activation can be done at different times. This is because the two steps are dependent on each other for activation of the protein.
Some proteins are innately photosensitive and function in the presence of light. Proteins known as opsins form the crux of the photosensitive proteins. These proteins are often found in the eye. In addition, many of these proteins function as ion channels and receptors. One example is when a certain wavelength of light is put onto certain channels, the blockage in the pore is relieved and allows ion transduction.
To uncage molecules, a photolysis system is required to cleave the covalent bond. An example system can consist of a light source (generally a laser or a lamp), a controller for the amount of light that enters, a guide for the light, and a delivery system. Often, the design function in such a way that a medium is met between the diffusing light that may cause additional, unwanted photolysis and light attenuation; both being significant problems with a photolysis system.