Anwander E H, Probst M M, Rode B M
Institut für Anorganische und Analytische Chemie, Universität Innsbruck, Austria.
Biopolymers. 1990 Mar-Apr;29(4-5):757-69. doi: 10.1002/bip.360290410.
The interaction of mono- and divalent metal ions with the nucleic acid base pairs A:T and G:C has been studied using ab initio self-consistent field Hartree-Fock computations with minimal basis sets. Energy-optimized structures of the two base pairs with a final base-base distance of L = 10.35 A have been determined and were further used in calculations on ternary complexes Mn+ - A:B together with previously computed coordination geometries of the cations at adenine (Ade), thymine (Thy), and guanine (Gua). Besides the binding energy of the various metal ions to the base pairs, changes in the stability of the H bonds between Ade and Thy or Gua and Cyt have been determined. Polarization effects of the metal ion on the ligand turned out to increase the binding between complementary bases. Regardless of the metal species, cation binding to Gua N(3) and Thy O(2) leads to a special increase in H-bond stability, whereas binding to Ade N(3) changes the H-bond stability least. Situated in between are the stabilizing effects caused by Gua and Ade N(7) coordination. A remarkable relation between the stability of the H bond and the distance from metal binding site to H bonds was found. This relationship has been rationalized in terms of partial charges of the atoms participating in H bonding, which can reveal the trend in the electrostatic part of total H bond energy. It can be shown that a short distance between coordination site and acceptor hydrogen increases the H-bond strength substantially, while a long distance shows minor effects as supposed. On the other hand, the opposite effect is observed for the influence of the distance between binding site and donor atom. A comparison of our findings with a new model of transition metal ion facilitated rewinding of denatured DNA proposed by S. Miller, D. VanDerveer, and L. Marzilli is given [(1985) J. Am. Chem. Soc. 107, 1048-1055].
利用从头算自洽场哈特里-福克计算方法和最小基组，研究了单价和二价金属离子与核酸碱基对A:T和G:C的相互作用。已确定了两个碱基对的能量优化结构，其最终碱基间距离L = 10.35 Å，并进一步用于计算三元络合物Mn⁺ - A:B，以及先前计算的阳离子在腺嘌呤（Ade）、胸腺嘧啶（Thy）和鸟嘌呤（Gua）处的配位几何结构。除了各种金属离子与碱基对的结合能外，还确定了Ade与Thy或Gua与Cyt之间氢键稳定性的变化。结果表明，金属离子对配体的极化作用增强了互补碱基之间的结合。无论金属种类如何，阳离子与Gua的N(3)和Thy的O(2)结合都会导致氢键稳定性特别增加，而与Ade的N(3)结合对氢键稳定性的影响最小。介于两者之间的是由Gua和Ade的N(7)配位引起的稳定作用。发现氢键稳定性与金属结合位点到氢键的距离之间存在显著关系。这种关系已根据参与氢键的原子的部分电荷进行了合理化解释，这可以揭示总氢键能量中静电部分的趋势。可以表明，配位位点与受体氢之间的短距离会显著增加氢键强度，而长距离的影响则如预期的那样较小。另一方面，对于结合位点与供体原子之间距离的影响，观察到相反的效果。将我们的研究结果与S. Miller、D. VanDerveer和L. Marzilli提出的变性DNA过渡金属离子促进复性的新模型进行了比较[（1985年）《美国化学会志》107，1048 - 1055]。
