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PHOTO‐CIDNP DETECTION OF PYRIMIDINE DIMER RADICAL CATIONS IN ANTHRAQUINONESULFONATE‐ SENSITIZED SPLITTING
Author(s) -
Young Tish,
Nieman Ron,
Rose Seth D.
Publication year - 1990
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1990.tb08664.x
Subject(s) - dimer , chemistry , photochemistry , photodissociation , radical ion , sulfonate , pyrimidine dimer , anthraquinone , ion , organic chemistry , sodium , dna , biochemistry , dna damage
— –Anthraquinone‐2‐sulfonate (AQS) photosensitizes pyrimidine dimer splitting. Electron abstraction from the dimer is thought to induce dimer splitting, but direct evidence for the existence and intermediacy of dimer radical cations has been lacking. By employing photochemically induced dynamic nuclear polarization, we have found emission signals in the NMR spectra of dimers upon photolysis of dimers in the presence of anthraquinone‐2‐sulfonate. The two dimers employed were ci?, syn‐thymine dimer in which the JV(l)‐positions were linked by a three‐carbon bridge and the N(3), N(3′)‐dimethyle derivative of that compound. The anthraquinone‐2‐sulfonate sensitized photochemically induced dynamic nuclear polarization spectrum of the methylated derivative exhibited an emission signal from the dimer‐C(6) hydrogens. This result implied the existence of a dimer radical cation ( mD + ) formed by electron abstraction by excited anthraquinone‐2‐sulfonate and nuclear spin sorting within a solvent caged radical ion pair [mD + AQS ‐ ]. Product pyrimidine photochemically induced dynamic nuclear polarization signals were also seen [enhanced absorption by C(6)‐hydrogens and emission by C(5)‐methyl groups]. Nuclear spin polarization in the product resulted from spin sorting in one or more of its precursors, including mD + . The results support the conclusion that dimer radical cations not only exist but are intermediates in the photosensitized splitting of pyrimidine dimers by anthraquinonesulfonate.