*Michael H. Patrick, The University of Texas at Dallas, P.O. Box 688, Richardson, TX 75080, U.S.A.
INDEPENDENCE OF PHOTOPRODUCT FORMATION ON DNA CONFORMATION*
Article first published online: 2 JAN 2008
Photochemistry and Photobiology
Volume 24, Issue 6, pages 507–513, December 1976
How to Cite
Patrick, M. H. and Gray, D. M. (1976), INDEPENDENCE OF PHOTOPRODUCT FORMATION ON DNA CONFORMATION. Photochemistry and Photobiology, 24: 507–513. doi: 10.1111/j.1751-1097.1976.tb06867.x
- Issue published online: 2 JAN 2008
- Article first published online: 2 JAN 2008
- Received 13 April 1976; accepted 30 June 1976
Abstract— In an ethanolic solution native T7 DNA can undergo conformational transitions from the B conformation (0% ethanol) to the C-like (60% w/w ethanol) and the A (80% w/w ethanol) conformations. We have investigated the formation of three classes of thymine-derived photoproducts in T7 DNA irradiated (280 nm) in the B, C-like, and A conformations, which were monitored by circular dichroism measurements. We find that the predominant class of thymine-derived photoproducts in any conformational state is cyclobutyl dipyrimidines. While the ‘spore product,’ 5-thyminyl-5,6-dihydrothymine, which belongs to another class of photoproductsf does form in native DNA in the A conformation, its yield in denatured DNA at 80% ethanol is the same as that in native DNA. The yield of pyrimidine adduct, a third photoproduct class, is a maximum at 50–60% ethanol. This effect of ethanol is probably not due to the ethanol-induced C-like conformation, however, since pyrimidine adduct formation is not enhanced when T7 DNA is irradiated in the C conformation in 6 M CsCl or in intact phage. We conclude from these and other data in the literature that the degree of hydration rather than the conformational state is the critical factor in determining which of the photoproducts will form in native DNA.