Department of Chemistry, University of Wyoming, 1000 East University Avenue, Laramie, Wyoming 82071, USA.
J Phys Chem B. 2011 Aug 25;115(33):10182-8. doi: 10.1021/jp2047213. Epub 2011 Aug 3.
Here, we report a highly sensitive and specific chiroptical detection method of condensed left-handed Z-DNA in the presence of canonical right-handed B-DNA. The selective formation of a left-handed cytosine-guanine oligonucleotide (CG ODN) in the presence of a right-handed adenine-thymine oligonucleotide (AT ODN) was induced by millimolar concentrations of NiCl(2) and confirmed by electronic circular dichroism. The nickel(II) induced B- to Z-DNA transition of the CG ODN was accompanied by the concurrent condensation of the Ni(II)-Z-DNA, as confirmed by resonance light scattering, transmission spectroscopy, and centrifugation. The selective condensation of the CG ODN allowed its separation from the AT ODN using centrifugation. No structural changes were observed for the AT ODN upon addition of Ni(II). Anionic nickel(II) meso-tetra(4-sulfonatophenyl) porphyrin (NiTPPS) spectroscopically detected the left-handed Z-DNA in the Z-DNA/B-DNA mixture via a strong exciton coupled circular dichroism (ECCD) signal induced in the porphyrin Soret band absorption region. The bisignate ECCD signal originates from the assembly of achiral porphyrins into helical arrays by intermolecular interactions with the condensed Z-DNA scaffold. No induced CD signal was observed for the Ni(II)-B-DNA-NiTPPS complex. Hence, an unambiguous spectroscopic recognition of Ni(II) induced condensed Z-DNA in the presence of B-DNA is possible. The sensitivity of this chiroptical method was as low as 5% of the Z-DNA (4.4 μmol base pair concentration) in the presence of 95% B-DNA (80 μmol). Thus, NiTPPS is a highly sensitive probe for applications in biosensing via the CD signal amplification.
在这里，我们报告了一种在存在典型右手 B-DNA 的情况下，对凝聚的左手 Z-DNA 进行高灵敏和特异的手性光学检测的方法。在毫米浓度的 NiCl2 存在下，通过电子圆二色性证实了右手 A-T 寡核苷酸（AT ODN）的存在诱导了左手 C-G 寡核苷酸（CG ODN）的选择性形成。镍（II）诱导的 CG ODN 的 B-ZDNA 转变伴随着 Ni(II)-Z-DNA 的同时凝聚，这一点通过共振光散射、透射光谱和离心得到了证实。CG ODN 的选择性凝聚允许其与 AT ODN 分离，使用离心。加入 Ni(II)后，AT ODN 没有观察到结构变化。阴离子镍（II）meso-四（4-磺基苯）卟啉（NiTPPS）通过在卟啉 Soret 带吸收区域诱导强激子偶合圆二色性（ECCD）信号，在 Z-DNA/B-DNA 混合物中光谱检测到左手 Z-DNA。双信号 ECCD 信号源于非手性卟啉通过与凝聚的 Z-DNA 支架的分子间相互作用组装成螺旋阵列。对于 Ni(II)-B-DNA-NiTPPS 配合物，没有观察到诱导的 CD 信号。因此，在手性光学方法中，有可能在存在 B-DNA 的情况下对手性识别 Ni(II)诱导的凝聚 Z-DNA。这种手性方法的灵敏度低至存在 95% B-DNA（80 μmol）时的 5%的 Z-DNA（4.4 μmol 碱基对浓度）。因此，NiTPPS 是一种通过 CD 信号放大应用于生物传感的高灵敏度探针。
