Department of Chemistry, Yeungnam University Dae-dong, Gyeongsan City, Gyeong-buk, 712-749, Republic of Korea.
J Phys Chem B. 2012 Aug 16;116(32):9619-26. doi: 10.1021/jp3041346. Epub 2012 Aug 3.
Zn(II) meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (ZnTMPyP) produced a unique linear dichroism (LD) spectrum when forming a complex with Z-form poly[d(G-C)(2)]. The spectrum was characterized by a large positive wavelength-dependent LD signal in the Soret absorption region. The magnitudes of LD in both the DNA and Soret band increased as the [porphyrin]/[DNA base] ratio increased and were larger by 20-40 times compared to the negative LD of the ZnTMPyP bound to B-form poly[d(G-C)(2)] and poly[d(A-T)(2)]. The angles calculated from LD were respectively 49° and 42° for B(x) and B(y) transitions of the porphyrin with respect to the local helix axis of Z-form poly[d(G-C)(2)]. The appearance of the unique LD spectrum for the Z-form poly[d(G-C)(2)] complex was accompanied by a bisignate circular dichroism spectrum in the Soret region, whose magnitude was proportional to the square of the porphyrin concentration, suggesting a stacking interaction between Z-form poly[d(G-C)(2)]-bound ZnTMPyP with other bound ZnTMPyP. From these observations, a conceivable binding mode of ZnTMPyP to Z-form poly[d(G-C)(2)] complex was proposed, in which ZnTMPyP binds at the major groove or across the groove. In contrast with Z-form poly[d(G-C)(2)], ZnTMPyP binds to poly[d(A-T)(2)] in a monomeric manner with the angles of 57° and 59° for the two porphyrin's transition moments with respect to the local polynucleotide helix axis. The polarized spectral properties of ZnTMPyP bound to B-form poly[d(G-C)(2)] coincide with the intercalated nonmetallic TMPyP, namely, a negative CD signal in the Soret band and a negative wavelength-dependent reduced LD signal, with a magnitude larger than that in the DNA absorption region in spite of its axial ligands.
锌(II)meso-四( N-甲基吡啶-4-基)卟啉(ZnTMPyP)与 Z 型聚[d(G-C)(2)]形成复合物时产生独特的线二色性(LD)光谱。该光谱的特征是在 Soret 吸收区域中存在大的、波长依赖的正 LD 信号。随着[卟啉]/[DNA 碱基]比的增加，DNA 和 Soret 带中的 LD 幅度增加，并且与 ZnTMPyP 结合到 B 型聚[d(G-C)(2)]和聚[d(A-T)(2)]的负 LD 相比，增加了 20-40 倍。从 LD 计算出的卟啉相对于 Z 型聚[d(G-C)(2)]的局部螺旋轴的 B(x)和 B(y)跃迁的角度分别为 49°和 42°。Z 型聚[d(G-C)(2)]复合物独特的 LD 光谱的出现伴随着 Soret 区域中双信号圆二色性光谱的出现，其幅度与卟啉浓度的平方成正比，表明 Z 型聚[d(G-C)(2)]-结合的 ZnTMPyP 与其他结合的 ZnTMPyP 之间存在堆积相互作用。从这些观察结果中，提出了 ZnTMPyP 与 Z 型聚[d(G-C)(2)]复合物的一种可以想象的结合模式，其中 ZnTMPyP 结合在大沟或跨越沟。与 Z 型聚[d(G-C)(2)]相反，ZnTMPyP 以单体形式与聚[d(A-T)(2)]结合，两个卟啉的跃迁矩相对于局部多核苷酸螺旋轴的角度分别为 57°和 59°。ZnTMPyP 与 B 型聚[d(G-C)(2)]结合的偏振光谱性质与嵌入的非金属 TMPyP 相吻合，即在 Soret 带中出现负 CD 信号和负波长依赖的减小的 LD 信号，尽管其轴向配体存在，但幅度大于 DNA 吸收区域中的幅度。
