INFLUENCE OF RELATIVE HUMIDITY ON PHOTOCHEMISTRY OF DNA FILMS

1. 1. Films of DNA were equilibrated at various relative humidities and then were irradiated with ultraviolet light at 25° so that changes in their photochemistry might be correlated with known conformational changes. 2. 2. Above 65% relative humidity the photochemical behavior of the films was the same as that in solution, with pyrimidine dimers, but few if any spore photoproducts, being formed. 3. 3. Below 65% relative humidity there was a 2-fold reduction in the yield of thymine dimers and a concomitant increase in the yield of spore photoproducts. 4. 4. These photochemical changes are consistent with the known conformational change in DNA films from the B form to a disorganized form as the relative humidity is reduced. © 1969.