作者:Li Wei、Ying Shao、Mi Zhou、Hong-Wen Hu、Guo-Yuan Lu
DOI:10.1039/c2ob25743b
日期:——
A new metal-free DNA cleaving reagent, bis-tacnorthoamide derivative 1 with two tacnorthoamide (tacnoa) units linked by a spacer containing anthraquinone, has been synthesized from triazatricyclo[5.2.1.04,10]decane and characterized by NMR and mass spectrometry. For comparison, the corresponding compounds mono-tacnorthoamide derivative 2 with one tacnorthoamide unit and 6 with two tacnorthoamide units linked by an alkyl (1,6-hexamethylene) spacer without anthraquinone have also been synthesized. The DNA-binding property investigated via fluorescence and CD spectroscopy suggests that compounds 1 and 2 have an intercalating DNA binding mode, and the apparent binding constants of 1, 2 and 6 are 1.3 × 107 M−1, 0.8 × 107 M−1 and 8 × 105 M−1, respectively. Agarose gel electrophoresis was used to assess plasmid pUC19 DNA cleavage activity promoted by 1, 2, 6 and parent tacnoa under physiological conditions, which gives rate constants kobs of 0.2126 ± 0.0055 h−1, 0.0620 ± 0.0024 h−1, 0.040 ± 0.0007 h−1 and 0.0043 ± 0.0002 h−1, respectively. The 50-fold and 15-fold rate acceleration over parent tacnoa is because of the anthraquinone moiety of compound 1 or 2 intercalating into DNA base pairs via a stacking interaction. Moreover, DNA cleavage reactions promoted by compound 1 give 5.3-fold rate acceleration over compound 6, which further demonstrates that the introduction of anthraquinone results in a large enhancement of DNA cleavage activity. In particular, DNA cleavage activity promoted by 1 bearing two tacnoa units is 3.3 times more effective than 2 bearing one tacnoa unit and the DNA cleavage by compound 1 was achieved effectively at a relatively low concentration (0.03 mM). This dramatic rate acceleration suggests the cooperative catalysis of the two positively charged tacnoa units in compound 1. The radical scavenger inhibition study and ESI-MS analysis of bis(2,4-dinitrophenyl) phosphate (BDNPP) and adenylyl(3′-5′)phosphoadenine (APA) cleavage in the presence of compound 1 suggest the cleavage mechanism would be via a hydrolysis pathway by cleaving the phosphodiester bond of DNA.
一种新型无金属DNA切割试剂,即由包含蒽醌的间隔基连接的两个tacnoa(tacnorthoamide)单元的双tacnoa衍生物1,已从三氮杂三环[5.2.1.04,10]癸烷合成并由NMR和质谱进行表征。为了比较,还合成了相应的单tacnoa衍生物2(含有一个tacnoa单元)和6(含有两个tacnoa单元,通过不含蒽醌的烷基(1,6-己二基)间隔基连接)。通过荧光和圆二色光谱调查的DNA结合性质表明,化合物1和2具有插入式DNA结合模式,其表观结合常数分别为1.3 × 10^7 M^-1、0.8 × 10^7 M^-1和8 × 10^5 M^-1。使用琼脂糖凝胶电泳评估在生理条件下由1、2、6和母体tacnoa促进的质粒pUC19 DNA切割活性,分别得到速率常数kobs为0.2126 ± 0.0055 h^-1、0.0620 ± 0.0024 h^-1、0.040 ± 0.0007 h^-1和0.0043 ± 0.0002 h^-1。相比于母体tacnoa,速率分别提高了50倍和15倍,这是由于化合物1或2的蒽醌部分通过堆叠相互作用插入到DNA碱基对中。此外,由化合物1促进的DNA切割反应的速率比化合物6提高了5.3倍,进一步证明蒽醌的引入大大增强了DNA切割活性。特别是,具有两个tacnoa单元的1促进的DNA切割活性比具有一个tacnoa单元的2高出3.3倍,并且在相对较低的浓度(0.03 mM)下有效实现了化合物1的DNA切割。这种显著的速率加速表明化合物1中的两个正电荷tacnoa单元之间的协同催化作用。自由基清除剂抑制研究和ESI-MS分析显示,在化合物1存在下,双(2,4-二硝基苯基)磷酸(BDNPP)和腺苷(3′-5′)磷酸腺苷(APA)的切割表明切割机制是通过水解途径切割DNA的磷酸二酯键。