Nonempirical calculations on dicopper(1+)-dioxygen: a possible model for oxyhemocyanin and oxytyrosinase active sites
Nonempirical calculations on dicopper(1+)-dioxygen: a possible model for oxyhemocyanin and oxytyrosinase active sites
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二铜(1)-双氧的非经验计算：氧血蓝蛋白和氧酪氨酸酶活性位点的可能模型
DOI：
10.1021/ic00018a013
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发表时间：
1991
影响因子：
4.6
通讯作者：
C. Giessner
中科院分区：
文献类型：
--
作者：
J. Maddaluno;C. Giessner
以两个铜阳离子（Cu (I)）与一个二氧分子相互作用为模型，作为氧血青素和氧酪氨酸酶活性位点的模型，进行了非经验计算，确定了该配合物最稳定的几何排列及其电子结构。封闭壳层SCF计算结果表明，配合物的最稳定电子构型在氧分子和铜阳离子之间的所有距离上并不相同。然而，对于两个相互作用实体的平行和垂直排列，配合物的最低能态是单线态，这与EPR数据一致。这一结果清楚地表明，所讨论的活性位点的磁性特征是由于通过唯一的双氧分子发生的超交换机制。此外，从本研究中获得的不同Cu-Cu距离的配合物的最稳定构象对应于两个金属离子之间的氧分子位置，这与[(L " Cu) 2-02] 2+模型系统的现有实验数据一致。我们的结果还表明，这种反式排列诱导了0-0键的重要延长。这一特征与拉曼和x射线数据一致，但当配合物具有顺-g-二氧构象时却没有发现，这进一步证明了我们简化模型的有效性。本文讨论了最稳定几何排列的电子结构与模型配合物的实验光谱数据以及氧血红素和氧化酪氨酸酶活性位点本身的关系，并讨论了这些酶的第二种可能的作用机制。
Nonempirical calculations on two copper cations (Cu (I)) interacting with a dioxygen molecule, taken as a model for the active site of oxyhemocyanin and oxytyrosinase, havebeen carried out to determine the most stable geometrical arrangement of this complex and its electronic structure. The results of closed-shell SCF computationsshow that the most stable electronic configuration of the complex is not the same for all distances between the oxygen molecule and the copper cations. Nevertheless, for the parallel as well as for the perpendicular arrangements of the two interacting entities, the lowest energy state of the complex is a singlet in agreement with EPR data. This result clearly shows that the magnetic characteristics of the active sites in question are due to a superexchange mechanism taking place through the sole dioxygen molecule. Moreover, the most stable conformation of the complexes obtained from this study for different Cu-Cu distances, corresponds to a location of the oxygen molecule between the two metal ions in agreement with the available experimental data on [(L „Cu) 2-02] 2+ model systems. Our results show also that this trans arrangement induces an important lengthening of the 0-0 bond. This feature, which is in agreement with Raman and X-ray data, is not found when the complex has the cis-g-dioxo conformation and provides further evidence for the validity of our simplified model. The electronic structure obtained for themost stable geometrical arrangement is discussed inrelation to the experimenal spectroscopic data concerning model complexes as well as oxyhemocyanin and oxytyrosinase active sites themselves and with respect to possible mechanisms of action for the second of these enzymes.