Hybrid molecules combining photoactivated aryl acetylenes and a dicationic lysine moiety cause the most efficient double-strand (ds) DNA cleavage known to date for a small molecule. In order to test the connection between the alkylating ability and the DNA-damaging properties of these compounds, we investigated the photoreactivity of three isomeric aryl–tetrafluoropyridinyl (TFP) alkynes with amide substituents in different positions (o-, m-, and p-) toward a model π-system. Reactions with 1,4-cyclohexadiene (1,4-CHD) were used to probe the alkylating properties of the triplet excited states in these three isomers whilst Stern–Volmer quenching experiments were used to investigate the kinetics of photoinduced electron transfer (PET). The three analogous isomeric lysine conjugates cleaved DNA with different efficiencies (34, 15, and 0% of ds DNA cleavage for p-, m-, and o-substituted lysine conjugates, respectively) consistent with the alkylating ability of the respective acetamides. The significant protecting effect of the hydroxyl radical and singlet oxygen scavengers to DNA cleavage was shown only with m-lysine conjugate. All three isomeric lysine conjugates inhibited human melanoma cell growth under photoactivation: The p-conjugate had the lowest CC50 (50% cell cytotoxicity) value of 1.49 × 10−7 M.
将光活化芳基乙炔和双阳离子赖氨酸基团结合的混合分子,致使目前已知对小分子而言最高效的双链DNA切割。为了测试烷化能力与这些化合物的DNA损伤特性之间的关联,我们研究了三种异构芳基-四氟吡啶基(TFP)炔烃的酰胺取代物在不同位置(o-、m-和p-)对模型π-系统的光反应性。使用1,4-环己二烯(1,4-CHD)反应来探测这三种异构体的三重激发态的烷化性质,而Stern-Volmer猝灭实验则用于研究光诱导电子转移(PET)的动力学。三种类似的异构赖氨酸共轭物以不同效率切割DNA(分别为p-、m-和o-取代的赖氨酸共轭物,ds DNA切割效率分别为34%、15%和0%),与相应乙酰胺的烷化能力一致。羟自由基和单线态氧清除剂对DNA切割的显著保护作用仅在m-赖氨酸共轭物中显示。所有三种异构赖氨酸共轭物在光活化下抑制人黑色素瘤细胞生长:其中p-共轭物的CC50 (50%细胞毒性)值最低,为1.49 × 10−7 M。