Every Alicia E, Russu Irina M
Department of Chemistry and Molecular Biophysics Program, Wesleyan University, Middletown, Connecticut 06459, USA.
J Phys Chem B. 2008 Jun 26;112(25):7689-95. doi: 10.1021/jp8005876. Epub 2008 May 31.
A large amount of experimental evidence is available for the effects of magnesium ions on the structure and the stability of the DNA double helix. Less is known, however, on how these ions affect the dynamics of the molecule and the stability of each individual base pair. The present work addresses these questions by a study of the DNA duplex [dCGCAGATCTGCG]2, and its interactions with magnesium ions using nuclear magnetic resonance (NMR) spectroscopy and proton exchange. Two-dimensional NMR experiments indicate that binding of magnesium to this DNA duplex does not affect its structure. However, even in the absence of structural changes, magnesium ions specifically affect the exchange properties of imino protons in the four GC/CG base pairs that are located in the interior of the double helix. These specific changes do not result from alterations in the rates of spontaneous opening of these base pairs. Instead, the changes most likely reflect an enhancement in the energetic propensity for spontaneous opening of the GC/CG base pairs that is induced by the binding of magnesium ions.
关于镁离子对DNA双螺旋结构和稳定性的影响，已有大量实验证据。然而，对于这些离子如何影响分子动力学以及每个碱基对的稳定性，人们了解较少。本研究通过对DNA双链体[dCGCAGATCTGCG]2及其与镁离子的相互作用进行核磁共振（NMR）光谱和质子交换研究，来解决这些问题。二维NMR实验表明，镁与该DNA双链体的结合不会影响其结构。然而，即使在没有结构变化的情况下，镁离子也会特异性地影响位于双螺旋内部的四个GC/CG碱基对中亚氨基质子的交换特性。这些特定变化并非由这些碱基对自发打开速率的改变引起。相反，这些变化很可能反映了镁离子结合诱导的GC/CG碱基对自发打开的能量倾向增强。
