Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States.
J Am Chem Soc. 2011 Mar 23;133(11):3863-8. doi: 10.1021/ja107033v. Epub 2011 Feb 24.
Quantum yields for charge transport across adenine tracts of increasing length have been measured by monitoring hole transport in synthetic oligonucleotides between photoexcited 2-aminopurine, a fluorescent analogue of adenine, and N(2)-cyclopropyl guanine. Using fluorescence quenching, a measure of hole injection, and hole trapping by the cyclopropyl guanine derivative, we separate the individual contributions of single- and multistep channels to DNA charge transport and find that with 7 or 8 intervening adenines the charge transport is a coherent, single-step process. Moreover, a transition occurs from multistep to single-step charge transport with increasing donor/acceptor separation, opposite to that generally observed in molecular wires. These results establish that coherent transport through DNA occurs preferentially across 10 base pairs, favored by delocalization over a full turn of the helix.
已通过监测 2-氨基嘌呤（腺嘌呤的荧光类似物）和 N(2)-环丙基鸟嘌呤之间的光激发后合成寡核苷酸中的空穴传输，测量了穿过腺嘌呤链的电荷传输的量子产率，腺嘌呤链的长度逐渐增加。使用荧光猝灭（空穴注入的一种衡量标准）和环丙基鸟嘌呤衍生物的空穴捕获，我们将 DNA 电荷传输的单步和多步通道的各个贡献分开，并发现有 7 或 8 个间隔腺嘌呤时，电荷传输是一个连贯的单步过程。此外，与通常在分子导线上观察到的情况相反，随着供体/受体分离的增加，电荷传输从多步到单步的转变发生。这些结果表明，通过 DNA 的相干传输优先发生在 10 个碱基对之间，这得益于螺旋的完整旋转的离域化。
