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the decrease in the injury to living cells caused by ultraviolet radiation when the cells are subsequently exposed to bright visible light.

Photoreactivation was discovered in 1948 by I. F. Kovalev in the USSR and A. Kelner and R. Dulbecco in the USA as a result of experiments carried out on infusoria paramecia, rotifers, fungous conidia, bacteria, and bacteriophages.

The basis of photoreactivation is the enzymatic splitting (into monomers) of the pyrimidine dimers formed in the deoxyribonucleic acid (DNA) under the action of ultraviolet radiation. Photoreactivation developed in the course of evolution as a protective adaptation against the lethal effects of the ultraviolet component of solar radiation. It is one of the most important forms of repair of injuries to the genetic system in living organisms.


Kovalev, 1. F. “Vliianie vidimogo uchastka spektra luchistoi energii na dinamiku patologicheskogo protsessa v kletke, povrezhdennoi ul’trafioletovymi luchami.” In Uchenye zapiski Ukrainskogo eksperimental’nogo instituta glaznykh boleznei, vol. 1. Odessa, 1949.
Vosstanovlenie kletok ot povrezhdenii. Moscow, 1963. (Translated from English.)
Smith, K., and P. Hanawalt. Molekuliarnaia fotobiologiia. Moscow, 1972. (Translated from English.)
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The observation of photoreactivation many years ago was one of the first indications to biologists that DNA repair mechanisms exist," says coauthor Johann Deisenhofer, a biochemist at the Howard Hughes Medical Institute at Southwestern Medical Center.
Synthesizing these impulses from within the medium, Schneider was to invert Levine's formula, turn from the summit to the base of our archives, from derivatives to the root, the negative, not for "reproduction" but for photoreactivation.
These include the production of UV-absorbing pigments, like melanin, that act as physical barriers, and DNA repair systems, such as photoreactivation (photolyase enzyme) and excision repair (base and nucleotide excision repair).