Can photobleaching be reversed?

Photobleaching may or may not be reversible depending on a number of factors. In most cases, photobleaching is irreversible. Once the molecule has been bleached, it cannot be restored to its original state. In some cases, photobleaching can be reversed, but this depends on the nature of the chromophore or fluorophore as well as the intensity and duration of the light exposure. The environment in which the molecule is located also plays a role in determining whether or not photobleaching can be reversed. There are techniques that can be used to prevent photobleaching. One such technique involves the use of two or more fluorescent molecules that can transfer energy to one another. FRAP or fluorescence recovery after photobleaching is another technique that involves intentionally bleaching a small region of a sample and then monitoring the recovery of fluorescence due to movement of surrounding intact probes into the bleached spot.