A Thermodynamic Model for Redox-Dependent Binding of Carbon Monoxide at Site-Differentiated, High Spin Iron Clusters.
A Thermodynamic Model for Redox-Dependent Binding of Carbon Monoxide at Site-Differentiated, High Spin Iron Clusters.
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DOI：
10.1021/jacs.8b01825
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发表时间：
2018-04-25
影响因子：
15
通讯作者：
Agapie T
中科院分区：
文献类型：
--
作者：
Arnett CH;Chalkley MJ;Agapie T
固氮酶的FeMo-辅因子对N2和CO的结合依赖于簇的氧化还原水平，但是纯氧化还原化学在多大程度上干扰了高自旋铁簇对π-酸的亲和力还没有很好的理解。在这里，我们报告了一系列的网站分化的铁簇，可逆地结合CO的氧化还原状态FeII 4通过FeIIFeIII 3。单电子氧化还原事件导致CO的亲和力（至多~400倍）和活化（νCO至多28 cm−1）的微小变化。氧化还原化学对这些高自旋，价定位的簇对CO的亲和力的影响很小，这与monoclonal和低自旋coclonal铁络合物的π-酸亲和力的大增强（105-1022倍）形成鲜明对比，其中氧化还原化学仅发生在配体结合位点。虽然电子负载在远离底物结合位点的金属中心对CO结合能的影响最小（约1 kcal·mol−1），但它为Fe III中心的CO结合提供了一个管道。事实上，来自这些远程位点的内部电子转移容纳了CO在Fe III上的结合，并伴随着氧化还原重组产生的小能量损失（约2.6 kcal·mol−1）。这些簇响应于配体结合而重新分配电子的容易性突出了FeMoco协调N2和CO的潜在途径，这可能发生在辅因子的氧化边缘上。
Binding of N2 and CO by the FeMo-cofactor of nitrogenase depends on the redox level of the cluster, but the extent to which pure redox chemistry perturbs the affinity of high spin iron clusters for π-acids is not well understood. Here, we report a series of site-differentiated iron clusters which reversibly bind CO in redox states FeII4 through FeIIFeIII3. One electron redox events result in small changes in the affinity for (at most ~400-fold) and activation of CO (at most 28 cm−1 for νCO). The small influence of redox chemistry on the affinity of these high spin, valence-localized clusters for CO is in stark contrast to the large enhancements (105-1022 fold) in π-acid affinity reported for monometallic and low spin bimetallic iron complexes, where redox chemistry occurs exclusively at the ligand binding site. While electron-loading at metal centers remote from the substrate binding site has minimal influence on the CO binding energetics (~1 kcal·mol−1), it provides a conduit for CO binding at an FeIII center. Indeed, internal electron transfer from these remote sites accommodates binding of CO at an FeIII, with a small energetic penalty arising from redox reorganization (~ 2.6 kcal·mol−1). The ease with which these clusters redistribute electrons in response to ligand binding highlights a potential pathway for coordination of N2 and CO by FeMoco, which may occur on an oxidized edge of the cofactor.
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影响因子：
4
作者：
Benito-Garagorri, David;Lagoja, Irene;Kirchner, Karl A.
通讯作者：
Kirchner, Karl A.
影响因子：
62.1
作者：
Hoffman, Brian M.;Lukoyanov, Dmitriy;Yang, Zhi-Yong;Dean, Dennis R.;Seefeldt, Lance C.
通讯作者：
Seefeldt, Lance C.
影响因子：
15
作者：
Creutz, Sidney E.;Peters, Jonas C.
通讯作者：
Peters, Jonas C.
影响因子：
4
作者：
Han, J;Coucouvanis, D
通讯作者：
Coucouvanis, D
影响因子：
2.9
作者：
Benton, PMC;Laryukhin, M;Seefeldt, LC
通讯作者：
Seefeldt, LC