Modeling the signatures of hydrides in metalloenzymes: ENDOR analysis of a Di-iron Fe(μ-NH)(μ-H)Fe core.
Modeling the signatures of hydrides in metalloenzymes: ENDOR analysis of a Di-iron Fe(μ-NH)(μ-H)Fe core.
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DOI：
10.1021/ja303739g
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发表时间：
2012-08-01
影响因子：
15
通讯作者：
Hoffman, Brian M.
中科院分区：
文献类型：
--
作者：
Kinney, R. Adam;Saouma, Caroline T.;Peters, Jonas C.;Hoffman, Brian M.
35 GHz脉冲EPR和ENDOR光谱的应用已经确定仿生模型络合物L3Fe(μ-NH)(μ-H)FeL3 (L3 = [PhB(CH2PPh2)3]-)络合物3是一种新型S = ½ III型混合价二铁II/III物质，其中不成对电子在两个铁中心之间平均共享。桥接酰亚胺的 1,2H 和 14,15N ENDOR 测量结果与两个桥接配体的烯丙基自由基分子轨道模型一致。晶体学特征 3 的 (μ-H) 和 (μ-NH) 质子都显示出“桥接”氢化物的特征，该氢化物在两个“锚定金属离子”之间基本上等距：菱形偶极相互作用张量，T ≈ [T, -T, 0]。用于将桥接 H 的各向异性相互作用描述为与“锚定”金属离子的点偶极耦合之和的点偶极模型以高精度再现了该特征，以及末端氢化物的轴向张量 T ≈ [-T, -T, 2T]，从而验证了模型和特征。该验证反过来为基于点偶极分析的分配提供了强有力的支持，即固氮酶的钼-铁辅助因子在已累积四个还原当量（E4）的催化中间体中包含两个[Fe-H--Fe]桥接氢化物片段。分析进一步揭示了 3 和 E4 中桥接氢化物的各向同性超精细耦合之间的互补相似性。该研究为除固氮酶外的多种还原金属酶中的氢化物的光谱研究奠定了基础。
The application of 35 GHz pulsed EPR and ENDOR spectroscopies has established that the biomimetic model complex L3Fe(μ-NH)(μ-H)FeL3 (L3 = [PhB(CH2PPh2)3]-) complex, 3, is a novel S = ½ type-III mixed-valence di-iron II/III species, in which the unpaired electron is shared equally between the two iron centers. 1,2H and 14,15N ENDOR measurements of the bridging imide are consistent with an allyl radical molecular orbital model for the two bridging ligands. Both the (μ-H) and the proton of the (μ-NH) of the crystallographically characterized 3 show the proposed signature of a ‘bridging’ hydride that is essentially equidistant between two ‘anchor metal ions: a rhombic dipolar interaction tensor, T ≈ [T, -T, 0]. The point-dipole model for describing the anisotropic interaction of a bridging H as the sum of the point-dipole couplings to the ‘anchor’ metal ions reproduces this signature with high accuracy, as well as the axial tensor of a terminal hydride, T ≈ [-T, -T, 2T], thus validating both the model and the signatures. This validation in turn lends strong support to the assignment, based on such a point-dipole analysis, that the molybdenum-iron cofactor of nitrogenase contains two [Fe-H--Fe] bridging-hydride fragments in the catalytic intermediate that has accumulated four reducing equivalents (E4). Analysis further reveals a complementary similarity between the isotropic hyperfine couplings for the bridging hydrides in 3 and E4. This study provides a foundation for spectroscopic study of hydrides in a variety of reducing metalloenzymes in addition to nitrogenase.
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影响因子：
2.2
作者：
Epel, B;Pöppl, A;Goldfarb, D
通讯作者：
Goldfarb, D
影响因子：
4.4
作者：
HUTCHISON, CA;MCKAY, DB
通讯作者：
MCKAY, DB
DOI：
10.1006/jmra.1994.1180
发表时间：
1994-09-01
期刊：
JOURNAL OF MAGNETIC RESONANCE SERIES A
影响因子：
--
作者：
HOFFMAN, BM;DEROSE, VJ;DAVOUST, CE
通讯作者：
DAVOUST, CE
影响因子：
1
作者：
Epel, B;Manikandan, P;Goldfarb, D
通讯作者：
Goldfarb, D
影响因子：
15
作者：
Brown, SD;Mehn, MP;Peters, JC
通讯作者：
Peters, JC