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Spectroscopic and electronic structure investigations of the oxygen-activating intermediates of ribonucleotide reductase.

机译：核糖核苷酸还原酶的氧激活中间体的光谱和电子结构研究。

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摘要

Circular dichroism (CD) and magnetic circular dichroism (MCD) data, combined with spin-Hamiltonian analysis and correlated with density functional theory (DFT) calculations allow identification of the active site geometries for biferrous wt- and W48F/D84E-R2 subunit of ribonucleotide reductase. This study probes the effect of varying the ligand set, the positions of coordinated water molecules and additional protein constraints on the geometry and energy of the binuclear site.; The geometric and electronic structure of the peroxo intermediate of the W48F/D84E-R2 variant was studied and related to the putative kinetically masked peroxo intermediate of wt-R2. The spectroscopic signatures of the W48F/D84E-R2 peroxo intermediate were found to be consistent only with the cis -μ-1,2 peroxo coordination geometry. DFT geometry optimizations using a model including the constraints imposed by the wt- and W48F/D84E-R2 active site ligand sets identifies cis-μ-1,2 peroxo as the most stable intermediate structure. This study produces new insight into the electronic structure of the experimentally defined peroxo intermediate, structurally similar model complexes and other biological biferric peroxo intermediates.; The high-valent intermediates of oxygen activation are poorly characterized and their structures are still a matter of debate. To investigate the nature of the high-valent bis-μ-oxo core, the spectroscopic properties and electronic structure of the structurally defined Fe2(III,IV) complex, [Fe 2O2(5-Et3-TPA)2](ClO4) 3 where 5-Et3-TPA=tris(5-ethyl-2-pyridylmethyl)amine were explored. Analysis of absorption, MCD, resonance Raman profiles and VTVH MCD saturation behavior allows transition assignments and calibration of density functional calculations. The C2h geometric distortion of the Fe 2O2 core is due to asymmetry in the capping ligand and results in a small (∼20%) difference in bond strength between adjacent Fe–O bonds. Density functional calculations also identify the orbital origins of the unique magnetic features of this core and identify the three singly-occupied π* metal-based orbitals that form strong superexchange pathways which lead to valence delocalization and the S = 32 ground state. Frontier molecular orbital (FMO) theory identifies these orbitals as key to the observed reactivity of this complex as they overlap with the substrate C–H bonding orbital in the best trajectory results for the high-valent enzyme intermediates are discussed.
机译：圆二色性（CD）和磁圆二色性（MCD）数据，结合自旋哈密顿分析并与密度泛函理论（DFT）计算相关，从而可以鉴定核糖核苷酸的重金属和W48F / D84E-R2亚铁的活性位点几何还原酶。这项研究探讨了改变配体组，配位水分子的位置以及其他蛋白质限制对双核位点的几何形状和能量的影响。研究了W48F / D84E-R2变体的过氧中间体的几何和电子结构，并与wt-R2的假定动力学掩蔽的过氧中间体有关。发现W48F / D84E-R2过氧中间体的光谱特征仅与顺-μ-1,2过氧配合基团一致。使用包含wt-和W48F / D84E-R2活性位点配体集的约束的模型进行的DFT几何优化确定了 cis -μ-1,2过氧化物为最稳定的中间结构。这项研究为实验定义的过氧中间体，结构相似的模型配合物和其他生物双铁过氧中间体的电子结构提供了新的见识。氧活化的高价中间体的表征很差，其结构仍是一个有争议的问题。为了研究高价bis-μ-oxo核的性质，结构定义的Fe 2 （III，IV）配合物[Fe 2 O 2 （5-Et 3 -TPA） 2 ]（ClO 4 ） 3 其中探索了5-Et 3 -TPA =三（5-乙基-2-吡啶基甲基）胺。通过分析吸收，MCD，共振拉曼曲线和VTVH MCD饱和行为，可以进行过渡分配和密度函数计算的校准。 Fe 2 O 2 核的C 2h 几何变形是由于封盖配体中的不对称性而导致的（<20％ ）相邻的Fe–O键之间的键强度差异。密度泛函计算还确定了该磁芯独特磁性特征的轨道起源，并确定了三个单独的基于π*金属的轨道，这些轨道形成了强的超交换路径，导致价态离域，并且S = < fr> 3 2 基态。前沿分子轨道（FMO）理论将这些轨道确定为该复合物观察到的反应性的关键，因为它们在高价酶中间体的最佳轨迹结果中与底物C–H键合轨道重叠，因此得到了讨论。

著录项

  • 作者

    Skulan, Andrew John.;

  • 作者单位

    Stanford University.;

  • 授予单位 Stanford University.;
  • 学科 Chemistry Analytical.
  • 学位 Ph.D.
  • 年度 2004
  • 页码 209 p.
  • 总页数 209
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化学;
  • 关键词

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