Fonseca Guerra Célia, van der Wijst Tushar, Bickelhaupt F Matthias
Theoretische Chemie, Scheikundig Laboratorium der Vrije Universiteit, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.
Chemistry. 2006 Apr 3;12(11):3032-42. doi: 10.1002/chem.200501301.
We have theoretically analyzed Watson-Crick guanine-cytosine (GC) base pairs in which purine-C8 and/or pyrimidine-C6 positions carry a substituent X = NH(-), NH(2), NH(3) (+) (N series), O(-), OH, or OH(2) (+) (O series), using the generalized gradient approximation (GGA) of density functional theory at the BP86/TZ2P level. The purpose is to study the effects on structure and hydrogen-bond strength if X= H is substituted by an anionic, neutral, or cationic substituent. We found that replacing X = H by a neutral substituent has relatively small effects. Introducing a charged substituent, on the other hand, led to substantial and characteristic changes in hydrogen-bond lengths, strengths, and hydrogen-bonding mechanism. In general, introducing an anionic substituent reduces the hydrogen-bond-donating and increases the hydrogen-bond-accepting capabilities of a DNA base, and vice versa for a cationic substituent. Thus, along both the N and O series of substituents, the geometric shape and bond strength of our DNA base pair can be chemically switched between three states, thus yielding a chemically controlled supramolecular switch. Interestingly, the orbital-interaction component in some of these hydrogen bonds was found to contribute to more than 49 % of the attractive interactions and is thus virtually equal in magnitude to the electrostatic component, which provides the other (somewhat less than) 51 % of the attraction.
我们使用密度泛函理论在BP86/TZ2P水平的广义梯度近似（GGA），从理论上分析了嘌呤-C8和/或嘧啶-C6位置带有取代基X = NH(-)、NH(2)、NH(3) (+)（N系列）、O(-)、OH或OH(2) (+)（O系列）的沃森-克里克鸟嘌呤-胞嘧啶（GC）碱基对。目的是研究如果将X = H替换为阴离子、中性或阳离子取代基时，对结构和氢键强度的影响。我们发现用中性取代基替换X = H的影响相对较小。另一方面，引入带电取代基会导致氢键长度、强度和氢键形成机制发生显著且独特的变化。一般来说，引入阴离子取代基会降低DNA碱基的氢键供体能力并增加其氢键受体能力，而阳离子取代基的情况则相反。因此，沿着N和O系列取代基，我们的DNA碱基对的几何形状和键强度可以在三种状态之间进行化学切换，从而产生一种化学控制的超分子开关。有趣的是，在其中一些氢键中，轨道相互作用成分对吸引力的贡献超过49%，因此其大小实际上与提供另外（略少于）51%吸引力的静电成分相当。
