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Abstract：
It was demonstrated that styrylquinolizinium derivatives may be applied as photoswitchable DNA ligands. At lower ligand:DNA ratios (≤1.5), these compounds bind to duplex DNA by intercalation, with binding constants ranging from K b = 4.1 × 104 M to 2.6 × 105 M (four examples), as shown by photometric and fluorimetric titrations as well as by CD and LD spectroscopic analyses. Upon irradiation at 450 nm, the methoxy-substituted styrylquinolizinium derivatives form the corresponding syn head-to-tail cyclobutanes in a selective [2 + 2] photocycloaddition, as revealed by X-ray diffraction analysis of the reaction products. These photodimers bind to DNA only weakly by outside-edge association, but they release the intercalating monomers upon irradiation at 315 nm in the presence of DNA. As a result, it is possible to switch between these two ligands and likewise between two different binding modes by irradiation with different excitation wavelengths.
摘要：
已证明苯乙烯基喹啉鎓衍生物可用作光开关DNA配体。在较低的配体：DNA比率（≤1.5），这些化合物通过嵌入结合双链DNA，结合常数范围为Kb=4.1×104M至2.6×105M（四个示例），如光度和荧光滴定以及CD和LD光谱分析所示。在450nm的照射下，甲氧基取代的苯乙烯基喹啉衍生物在选择性[2+2]光环加成中形成相应的顺式头对尾环丁烷，如反应产物的X射线衍射分析所揭示。这些光二聚体仅通过外部边缘缔合与DNA弱结合，但是它们在DNA存在下在315nm处照射时释放嵌入单体。因此,通过用不同的激发波长照射,可以在这两种配体之间以及同样在两种不同的结合模式之间切换。
