6299-61-2Relevant articles and documents
Radiation-induced and photosensitized splitting of c5-c5′-linked dihydrothymine dimers. 2. conformational effects on the reductive splitting mechanism
Ito, Takeo,Shinohara, Hideki,Hatta, Hiroshi,Fujita, Shin-ichi,Nishimoto, Sei-ich
, p. 2886 - 2893 (2007/10/03)
Radiation-induced and photosensitized reductive splitting of stereoisomeric C5-C5′-linked dihydrothymine dimers (1a,b[meso], meso compound of (5R,5′S)- and (5S,5′R)-bi-5,6-dihydrothymines; 1a,b[rac], racemic compound of (5R,5′R)- and (5S,5′S)-bi-5,6-dihydrothymines) in aqueous solution were studied to compare with the one-electron oxidative splitting mechanism and the photorepair reaction of cyclobutane pyrimidine photodimers. Reacting with radiation-chemically and photochemically generated hydrated electrons or with photoexcited reduced form of flavin adenine dinucleotide (*FADH-), the C5-C5′-linked dihydrothymine dimers 1a,b produced the corresponding 5,6-dihydrothymine derivatives (3a,b) along with the thyrnine monomers (2a,b) in minor yields. Both the product and laser flash photolysis studies indicated that oneelectron adducts of the C5-C5′-linked dimers 1a,b undergo C5-C5′-bond cleavage to generate the 5,6-dihydrothymin-5-yl radicals (5a,b) and the 5,6-dihydrothymine C5-anions (6a,b) resulting in the formation of 3a,b by facile protonation at C5. In the reduction by *FADH-, splitting of the 5,6-dihydro-1-methylthymine dimer 1a[meso] into the monomer 2a was more efficient than that of the racemic isomer 1a[rac]. Conformational analysis by NMR of 1a[meso] and 1a[rac] in solution suggested that 1a[meso] may favor a "closed-shell" conformation and undergo one-electron reduction to form 5a and 6a, whereas 1a[rac] may be in a "opened-shell" conformation and undergo successive two-electron reduction by *FADH- to produce 2 equiv of 6a as a precursor of 3a.
