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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Stabilization Energies of the Hydrogen-Bonded and Stacked Structures of Nucleic Acid Base Pairs in the Crystal Geometries of CG,AT,and AC DNA Steps and in the NMR Geometry of the 5'-d(GCGAAGC)-3' Hairpin:Complete Basis Set Calculations at the MP2 and
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Stabilization Energies of the Hydrogen-Bonded and Stacked Structures of Nucleic Acid Base Pairs in the Crystal Geometries of CG,AT,and AC DNA Steps and in the NMR Geometry of the 5'-d(GCGAAGC)-3' Hairpin:Complete Basis Set Calculations at the MP2 and

机译：CG，AT和AC DNA步骤的晶体几何结构以及5'-d（GCGAAGC）-3'发夹的NMR几何结构中核酸碱基对的氢键键合和堆叠结构的稳定能：完全基组MP2和

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Stabilization energies of the H-bonded and stacked structures of a DNA base pair were studied in the crystal structures of adenine-thymine,cytosine-guanine,and adenine-cytosine steps as well as in the 5'-d(GCGAAGC)-3' hairpin (utilizing the NMR geometry).Stabilization energies were determined as the sum of the complete basis set (CBS) limit of MP2 stabilization energies and the DELTAE~(CCSD(T)) - DELTAE~(MP2) correction term evaluated with the 6-31G~*(0.25) basis set.The CBS limit was determined by a two-point extrapolation using the aug-cc-pVXZ basis sets for X = D and T.While the H-bonding energies are comparable to those of base pairs in a crystal and a vacuum,the stacking energies are considerably smaller in a crystal.Despite this,the stacking is still important and accounts for a significant part of the overall stabilization.It contributes equally to the stability of DNA as does H-bonding for AT-rich DNAs,while in the case of GC-rich DNAs it forms about one-third of the total stabilization.Interstrand stacking reaches surprisingly large values,well comparable to the intrastrand ones,and thus contributes significantly to the overall stabilization.The hairpin structure is characterized by significant stacking,and both guanine...cytosine pairs possess stacking energies larger than 11.5 kcal/mol.A high portion of stabilization in the studied hairpin comes from stacking (similar to that found for AT-rich DNAs) despite the fact that it contains two GC Watson-Crick pairs having very large H-bonding stabilization.The DFT/B3LYP/6-31G~(**) method yields satisfactory values of interaction energies for H-bonded structures,while it fails completely for stacking.
机译：在腺嘌呤-胸腺嘧啶，胞嘧啶-鸟嘌呤和腺嘌呤-胞嘧啶台阶以及5'-d（GCGAAGC）-3'的晶体结构中研究了DNA碱基对的H键键合和堆叠结构的稳定能。发夹（利用NMR几何形状）。稳定能确定为MP2稳定能的完整基集（CBS）极限与DELTAE〜（CCSD（T））-DELTAE〜（MP2）校正项之和的和（6） -31G〜*（0.25）基集.CBS极限是通过aug-cc-pVXZ基集通过两点外推法确定的，其中X = D和T.H键合能与碱基对相当在晶体和真空中，晶体中的堆叠能量要小得多。尽管如此，堆叠仍然很重要，并占了整体稳定性的重要部分。与H键合一样，它同样有助于DNA的稳定性。富含AT的DNA，而富含GC的DNA约占总DNA的三分之一链间堆叠达到惊人的大值，与链内堆叠相当，因此对整体稳定性有显着贡献。发夹结构的特征是显着堆叠，并且两个鸟嘌呤...胞嘧啶对都具有大于11.5 kcal /的堆叠能。摩尔尽管所包含的两个GC Watson-Crick对具有非常大的H键稳定度，但它在发夹中的稳定度很大一部分来自堆叠（类似于富含AT的DNA的发现）.DFT / B3LYP / 6-31G〜（**）方法对于氢键结构产生令人满意的相互作用能值，但不能完全堆叠。

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