Efficient Photocleavage of DNA by Cationic Porphyrin. Acridine Hybrids with the Effective Length of Diamino Alkyl Linkage.
作者:Yoshinobu ISHIKAWA、Aya YAMASHITA、Tadayuki UNO
DOI:10.1248/cpb.49.287
日期:——
Positively charged porphyrins bearing an acridine with various lengths of diamino alkyl linkage, 5-[4-[(6-chloro-2-methoxy-9-acridyl)aminoalkylaminocarbonyl]phenyl]-10, 15, 20-tris(4-N-methylpyridiniumyl)porphine triiodide, alkyl=ethyl, butyl, hexyl, or octyl, were synthesized. They exhibited more enhanced photocleavage activity of pUC18 plasmid DNA than TMPyP, meso-tetrakis(4-N-methylpyridiniumyl)porphine, which is well known to bind to DNA tightly and to cleave DNA effectively; the hybrid linked with the hexamethylene chain showed particularly high activity. An equilibrium dialysis experiment demonstrated that the binding ability of the hybrids to calf thymus (CT) DNA correlated quantitatively with the photocleavage activity. The lack of the substantial red-shift of the Soret maxima of the hybrids through the titration with CTDNA denied the intercalative binding of the porphyrin part. In their circular dichroism (CD) spectral change on binding to CTDNA, two negative peaks appeared at 275 nm and at 285-290 nm in the UV range. The latter negative peak was observed for hybrids, but not for TMPyP, and thus we assigned it to induced CD (ICD) derived from intercalation of acridine chromophore. In the visible range, the hybrids showed only a positive peak around their Soret maxima, and this feature suggested the porphyrin moiety lay in the DNA groove. In addition, the length of the linker markedly influenced the ellipticity of their visible ICD, suggesting that the proximity of the porphyrin moiety to DNA was greatly affected by the linker.
合成了带有不同长度二氨基烷基连接的正电荷卟啉,5-[4-[(6-氯-2-美克氧基-9-氨基苯并吡啶)氨基烷基氨基甲酰基]苯基]-10, 15, 20-三(4-N-甲基吡啶鎓)卟啉三碘化物,烷基=乙基、丁基、己基或辛基。与已知能够紧密结合DNA并有效裂解DNA的TMPyP(美索-四(4-N-甲基吡啶鎓)卟啉)相比,它们在对pUC18质粒DNA的光裂解活性上表现出更强的增强效果;与己基链连接的杂交物表现出特别高的活性。一项平衡透析实验表明,杂交物与小牛胸腺(CT)DNA的结合能力与其光裂解活性之间存在定量关联。通过与CTDNA的滴定,杂交物的索雷特峰值没有发生显著红移,否定了卟啉部分的嵌入式结合。在与CTDNA结合时,它们在圆二色性(CD)光谱变化中,在紫外范围内出现了275 nm和285-290 nm的两个负峰。后者的负峰仅在杂交物中观察到,而在TMPyP中没有,因此我们将其归因于由氨基苯并吡啶的嵌入引起的诱导CD(ICD)。在可见光范围内,杂交物仅在其索雷特峰值附近显示出一个正峰,这一特征表明卟啉部分位于DNA的凹沟中。此外,连接链的长度显著影响了其可见ICD的椭圆率,表明卟啉部分与DNA的接近程度受到了连接链的极大影响。