Premium
WAVELENGTH DEPENDENCE OF THE PHOTODECOMPOSITION OF 2‐DEOXYTHYMIDYLYL‐(3′→5′)‐2′‐DEOXYTHYMIDINE, dTpdT, IRRADIATED BY MONOCHROMATIC VACUUM‐UV PHOTONS ABOVE 50 nm
Author(s) -
Mikio Saitou
Publication year - 1993
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.1751-1097.1993.tb02954.x
Subject(s) - thymine , chemistry , photochemistry , deoxyribose , irradiation , wavelength , decomposition , ionization , analytical chemistry (journal) , chromatography , nucleic acid , organic chemistry , optics , physics , biochemistry , dna , ion , nuclear physics
— 2′‐Deoxythymidylyl‐(3′→5′)‐2′‐deoxythymidine, dTpdT, was irradiated in solids with monochromatic synchrotron radiations at wavelengths between 50 and 260 nm, in order to investigate the photodecomposition mode of dTpdT in the wavelength region around and above the ionization potential. The photoproducts were separated and quantitatively analyzed by high‐performance liquid chromatography. The results of the present experiment were as follows: (1) Below 210 nm the major photoproducts were three decomposition products (thymine [Thy], 2′‐deoxythymidine 5′‐monophosphate [5′‐dTMP] and 2′‐deoxythymidine 3′‐monophosphate [3′‐dTMP]), whereas above 210 nm these decomposition products were under the detection limit and trace amounts of cyclobutane thymine (Thy) dimers (cis‐syn and trans‐syri) and thymine(6–4) photoproduct were detected. 2′‐Deoxythymidine (dThd) was not detected at any wavelengths tested. (2) The yields of the three decomposition products had very similar wavelength dependence with each other: the yields increased exponentially with the decrease in the wavelength down to 100 nm, whereas they were relatively constant below 100 nm. (3) The ratios of the yields of dTMP (5′‐dTMP plus 3′‐dTMP) to the yield of Thy showed minor deviations from 1 both above and below the ionization potential of deoxyribose (9.7 eV, or 130 nm: Tasaki et al., 1990, J. Am. Chem. Soc. 112,538–548): the average ratio was 0.85 between 50 and 100 nm and 1.30 between 120 and 210 nm. The ratios should be 1 if photodecomposition is induced only by deoxyribose decomposition. These ratios therefore indicated that the major photodecomposition mode of dTpdT was the destruction of deoxyribose moieties and additional minor modes caused the deviation from 1. (4) The yield of 5′‐dTMP was twice as much as the yield of 3′‐dTMP, showing that the deoxyribose residue without the 5′‐phosphate group was more sensitive than the deoxyribose residue with the 5′‐phosphate group.