Z-Form DNA Specific Binding Geometry of Zn(II) meso-Tetrakis(N-methylpyridinium-4-yl)porphyrin Probed by Linear Dichroism Spectroscopy
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- 作者：Lindan Gong ; Yoon Jung Jang ; Jinheung Kim ; Seog K. Kim
- 刊名：The Journal of Physical Chemistry B
- 出版年：2012
- 出版时间：August 16, 2012
- 年：2012
- 卷：116
- 期：32
- 页码：9619-9626
- 全文大小：463K
- 年卷期：v.116,no.32(August 16, 2012)
- ISSN：1520-5207
文摘
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鈥?0 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掳 and 42掳 for Bx and By 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掳 and 59掳 for the two porphyrin鈥檚 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.