About Photolyase enzyme ... Hope that will help

The Ohio State University study revealed how the enzyme photolyase uses energy from visible light to repair UV damage.

This enzyme is missing in all mammals, including humans, although all plants and all other animals have it. Greater understanding of how photolyase works could one day lead to drugs that help repair UV damage in human DNA.

In the online edition of the Proceedings of the National Academy of Sciences, Dongping Zhong and his colleagues report experimental evidence of what scientists have long suspected -- that visible light excites the photolyase molecule and boosts the energy of electrons in its atoms. This in turn enables the enzyme to inject an electron into the DNA molecule at the UV damage site temporarily to perform repairs.

They also report something that was unexpected: Water plays a key role in the process, by regulating how long the donated electron stays inside the damage site before returning to the photolyase molecule.