Santangelo Maria Grazia, Medina-Molner Alfredo, Schweiger Arthur, Mitrikas George, Spingler Bernhard
Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland.
J Biol Inorg Chem. 2007 Aug;12(6):767-75. doi: 10.1007/s00775-007-0230-1. Epub 2007 Apr 6.
Simple copper salts are known to denature poly d(GC). On the other hand, copper complexes of substituted 1,4,7,10,13-pentaazacyclohexadecane-14,16-dione are able to convert the right-handed B form of the same DNA sequence to the corresponding left-handed Z form. A research program was started in order to understand why Cu(II) as an aquated ion melts DNA and induces the conformational change to Z-DNA in the form of an azamacrocyclic complex. In this paper, we present a continuous wave and pulse electron paramagnetic resonance study of the mononucleotide model system Cu(II)-guanosine 5'-monophosphate . Pulse EPR methods like electron-nuclear double resonance and hyperfine sublevel correlation spectroscopy provide unique information about the electronic and geometric structure of this model system through an elaborate mapping of the hyperfine and nuclear quadrupole interactions between the unpaired electron of the Cu(II) ion and the magnetic nuclei of the nucleotide ligand. It was found that the Cu(II) ion is directly bound to N7 of guanosine 5'-monophosphate and indirectly bound via a water of hydration to a phosphate group. This set of experiments opens the way to more detailed structural characterization of specifically bound metal ions in a variety of nucleic acids of biological interest, in particular to understand the role of the metal-(poly)nucleotide interaction.
已知简单的铜盐会使聚d(GC)变性。另一方面，取代的1,4,7,10,13-五氮杂环十六烷-14,16-二酮的铜配合物能够将相同DNA序列的右手B型转化为相应的左手Z型。为了理解为什么作为水合离子的Cu(II)会使DNA熔化并以氮杂大环配合物的形式诱导其构象转变为Z-DNA，我们启动了一项研究计划。在本文中，我们展示了对单核苷酸模型系统Cu(II)-鸟苷5'-单磷酸的连续波和脉冲电子顺磁共振研究。像电子-核双共振和超精细亚能级相关光谱这样的脉冲EPR方法，通过精心绘制Cu(II)离子的未成对电子与核苷酸配体的磁性核之间的超精细和核四极相互作用，提供了关于该模型系统的电子和几何结构的独特信息。研究发现，Cu(II)离子直接与鸟苷5'-单磷酸的N7结合，并通过一个水合水分子间接与一个磷酸基团结合。这一系列实验为更详细地表征具有生物学意义的各种核酸中特异性结合的金属离子的结构开辟了道路，特别是有助于理解金属-(多)核苷酸相互作用的作用。
