Datta Bhaskar, Schmitt Christoph, Armitage Bruce A
Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213-3890, USA.
J Am Chem Soc. 2003 Apr 9;125(14):4111-8. doi: 10.1021/ja028323d.
DNA guanine (G) quadruplexes are stabilized by an interesting variation of the hydrogen-bonding schemes encountered in nucleic acid duplexes and triplexes. In an attempt to use this mode of molecular recognition, we target a dimeric G-quadruplex formed by the Oxytricha nova telomeric sequence d(G(4)T(4)G(4)) with a peptide nucleic acid (PNA) probe having a homologous rather than complementary sequence. UV-vis and CD spectroscopy reveal that a stable hybrid possessing G-quartets is formed between the PNA and DNA. The four-stranded character of the hybrid and the relative orientation of the strands is determined by fluorescence resonance energy transfer (FRET) experiments. FRET results indicate that (i) the two PNA strands are parallel to each other, (ii) the two DNA strands are parallel to each other, and (iii) the 5'-termini of the DNA strands align with the N-termini of the PNA strands. The resulting PNA(2)-DNA(2) quadruplex shows a preference of Na(+) over Li(+) and displays thermodynamic behavior consistent with alternating PNA and DNA strands in the hybrid. The formation of this novel supramolecular structure demonstrates a new high-affinity DNA recognition mechanism and expands the scope of molecular recognition by PNA.
DNA鸟嘌呤（G）四链体通过核酸双链体和三链体中氢键模式的有趣变化而得以稳定。为了利用这种分子识别模式，我们用具有同源而非互补序列的肽核酸（PNA）探针靶向由新大草履虫端粒序列d(G(4)T(4)G(4))形成的二聚体G-四链体。紫外可见光谱和圆二色光谱表明，PNA与DNA之间形成了具有G-四重体的稳定杂交体。通过荧光共振能量转移（FRET）实验确定了杂交体的四链特征和链的相对取向。FRET结果表明：（i）两条PNA链彼此平行；（ii）两条DNA链彼此平行；（iii）DNA链的5'末端与PNA链的N末端对齐。所得的PNA(2)-DNA(2)四链体对Na(+)的偏好超过Li(+)，并表现出与杂交体中PNA和DNA链交替一致的热力学行为。这种新型超分子结构的形成证明了一种新的高亲和力DNA识别机制，并扩展了PNA的分子识别范围。
