Adam W, Groer P, Mielke K, Saha-Möller C R, Hutterer R, Kiefer W, Nagel V, Schneider F W, Ballmaier D, Schleger Y, Epe B
Institute of Organic Chemistry, University of Würzburg, Germany.
Photochem Photobiol. 1997 Jul;66(1):26-33. doi: 10.1111/j.1751-1097.1997.tb03134.x.
The acridine and phenanthridine hydroperoxides 3 and 7 were synthesized as photochemical hydroxyl radical sources for oxidative DNA damage studies. The generation of hydroxyl radicals upon UVA irradiation (lambda = 350 nm) was verified by trapping experiments with 5,5-dimethyl-1-pyrroline N-oxide and benzene. The enzymatic assays of the damage in cell-free DNA from bacteriophage PM2 caused by the acridine and phenanthridine hydroperoxides 3 and 7 under near-UVA irradiation revealed a wide range of DNA modifications. Particularly, extensive single-strand break formation and DNA base modifications sensitive to formamidopyrimidine DNA glycosylase (Fpg protein) were observed. In the photooxidation of calf thymus DNA, up to 0.69 +/- 0.03% 8-oxo-7,8-dihydroguanine was formed by the hydroperoxides 3 and 7 on irradiation, whose yield was reduced up to 40% in the presence of the hydroxyl radical scavengers mannitol and tert-butanol. The acridine and phenanthridine hydroperoxides 3 and 7 also induce DNA damage through the type I photooxidation process, for which photoinduced electron transfer from 2'-deoxyguanosine to the singlet states of 3 and 7 was estimated by the Rehm-Weller equation to possess a negative Gibb's free energy of ca -5 kcal/ mol. Control experiments with the sensitizers acridine 1 and the acridine alcohol 4 in calf thymus and PM2 DNA confirmed the photosensitizing propensity of the UVA-absorbing chromophores. The present study emphasizes that for the development of selective and efficient photochemical hydroxyl radical sources, chromophores with low photosensitizing ability must be chosen to avoid type I and type II photooxidation processes.
吖啶和菲啶氢过氧化物3和7被合成为用于氧化DNA损伤研究的光化学羟基自由基源。通过用5,5-二甲基-1-吡咯啉N-氧化物和苯进行捕获实验，验证了UVA照射（λ = 350 nm）时羟基自由基的产生。对吖啶和菲啶氢过氧化物3和7在近UVA照射下引起的噬菌体PM2无细胞DNA损伤的酶促分析揭示了广泛的DNA修饰。特别地，观察到大量单链断裂的形成以及对甲酰胺嘧啶DNA糖基化酶（Fpg蛋白）敏感的DNA碱基修饰。在小牛胸腺DNA的光氧化过程中，氢过氧化物3和7在照射时形成高达0.69±0.03%的8-氧代-7,8-二氢鸟嘌呤，在存在羟基自由基清除剂甘露醇和叔丁醇的情况下，其产率降低高达40%。吖啶和菲啶氢过氧化物3和7也通过I型光氧化过程诱导DNA损伤，根据Rehm-Weller方程估计，从2'-脱氧鸟苷到3和7的单线态的光诱导电子转移具有约-5 kcal/mol的负吉布斯自由能。用敏化剂吖啶1和吖啶醇4在小牛胸腺和PM2 DNA中进行的对照实验证实了吸收UVA的发色团的光敏倾向。本研究强调，为了开发选择性和高效的光化学羟基自由基源，必须选择光敏能力低的发色团以避免I型和II型光氧化过程。
