title: The significance of the Dewar valence photoisomer as a UV radiation-induced DNA photoproduct in marine microbial communities.
abstract: Induction of pyrimidine dimers in DNA by solar UV radiation has drastic effects on microorganisms. To better define the nature of these DNA photoproducts in marine bacterioplankton and eukaryotes, a study was performed during a cruise along a latitudinal transect in the Pacific Ocean. The frequency of all possible cyclobutane pyrimidine dimers, pyrimidine (6-4) pyrimidone photoproducts (64PPs) and their related Dewar valence isomers (DEWs) was determined by high-performance liquid chromatography-mass spectrometry. Studied samples were bacterioplankton and eukaryotic fractions isolated from sea water either collected before sunrise or exposed to ambient sunlight from sunrise to sunset. Isolated DNA dosimeters were also exposed to daily sunlight for comparison purposes. A first major result was the observation in all samples of large amounts of DEWs, a class of photoproducts rarely considered outside photochemical studies. Evidence was obtained for a major role of UVA in the formation of these photoisomerization products of 64PPs. Considerations on the ratio between the different classes of photoproducts in basal and induced DNA damage suggests that photoenzymatic repair (PER) is an important DNA repair mechanism used by marine microorganisms occupying surface seawater in the open ocean. This result emphasizes the biological role of DEWs which are very poor substrate for PER.
authors: Center for Radiological Research, Columbia University, New York, NY, USA.
authors: Jarah A
authors: JA
authors: Meador
authors: Amy J
authors: AJ
authors: Baldwin
authors: J Dean
authors: JD
authors: Pakulski
authors: Wade H
authors: WH
authors: Jeffrey
authors: David L
authors: DL
authors: Mitchell
authors: Thierry
authors: T
authors: Douki
mesh_terms: D002851:Chromatography, High Pressure Liquid; D000458:Cyanobacteria / Q000235:genetics / Q000528:radiation effects; D018736:DNA Adducts / Q000235:genetics* / Q000302:isolation & purification; D004249:DNA Damage; D004260:DNA Repair; D004269:DNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D018744:DNA, Plant / Q000235:genetics / Q000302:isolation & purification; D007536:Isomerism; D010140:Pacific Ocean; D010839:Phytoplankton / Q000235:genetics / Q000528:radiation effects; D011740:Pyrimidine Dimers / Q000235:genetics*; D012623:Seawater / Q000382:microbiology; D013472:Sunlight; D053719:Tandem Mass Spectrometry; D014466:Ultraviolet Rays; D014871:Water Microbiology
chemical_list: D018736:DNA Adducts; D004269:DNA, Bacterial; D018744:DNA, Plant; D011740:Pyrimidine Dimers