20545-68-0

Upstream product

• 41398-83-8 C₂₀H₂₈N₄O₁₀ 
• 50-89-5 thymidine 
• 87367-14-4 thymidilyl(3'-5')thymidine 
• 20545-93-1 (5-hydroxy-5,6-dihydrothyminyl)-(6-4')(5'-methyl-1',2'-dihydropyrimidin-2'-one) 

Relevant academic research and scientific papers

The (5-4) and (6-4) adducts of 1-methylthymine and their Dewar valence isomers

Previous studies of the photochemical reaction of 1-methylthymine (MeT) in frozen aqueous solution have indicated that four cyclobutane type dimers are formed. We have restudied this system and have found that, in addition to cyclobutane dimers, both a (5-4) adduct and a (6-4) adduct of MeT are formed in significant amounts. Upon standing in aqueous solution, the (5-4) adduct is susceptible to reaction to form an isomeric form of the parent adduct, possibly via ring-opening and closure reactions at C-6 of the saturated pyrimidine ring component of the adduct. Irradiation of each of these three adducts with UVB light produces a pair of Dewar-type adducts. The nine products were individually characterized by mass spectrometry, proton NMR spectroscopy and UV spectroscopy. A less comprehensive study showed that irradiation of thymidine in frozen aqueous solution produces a diastereomeric pair of (5-4) adducts, along with the previously known diastereomeric pair of (6-4) adducts. Irradiation of 1-methylthymine (center) at 254 nm in frozen aqueous solution produces, in addition to cyclobutane dimers, both a (6-4) adduct (left) and a (5-4) adduct (right). The initially formed (5-4) adduct is unstable toward thermal conversion to another isomeric (5-4) adduct. Irradiation of each of these adducts in fluid solution with UVB results in the formation of two Dewar valence isomers. Similarly, irradiation of thymidine, frozen in ice at -78.5°C, produces a diastereomeric pair of (5-4) adducts, along with a corresponding pair of previously known (6-4) adducts.

Measurement of Pyrimidine (6-4) Photoproducts in DNA by a Mild Acidic Hydrolysis-HPLC Fluorescence Detection Assay

Pyrimidine (6-4) pyrimidone photoproducts constitute one of the major classes of DNA lesions induced by far-UV irradiation. However, their biological role remains difficult to assess partly because of the lack of a specific and sensitive assay for monitoring their formation in DNA. Here is presented a measurement method based on the release of the (6-4) base adducts from DNA followed by an HPLC separation associated with a sensitive and specific fluorescence detection. The quantitative and mechanistic aspects of the chemical hydrolysis, based on the use of hydrogen fluoride stabilized in pyridine, were investigated, using dinucleoside monophosphate (6-4) photoproducts as model compounds. The final hydrolysis products were isolated and characterized by UV, fluorescence, mass, and 1H NMR spectroscopies. Application of the assay to far-UV irrradiated calf thymus DNA provided information on the sequence effect on the rate of formation of three of the four possible bipyrimidine (6-4) photoproducts.