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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electron Spin-Lattice Relaxation Measurement of the 3Fe-4S (S-3) Cluster in Succinate: Ubiquinone Reductase from Paracoccus Denitrificans. A Detailed Analysis Based on a Dipole-Dipole Interaction Model
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Electron Spin-Lattice Relaxation Measurement of the 3Fe-4S (S-3) Cluster in Succinate: Ubiquinone Reductase from Paracoccus Denitrificans. A Detailed Analysis Based on a Dipole-Dipole Interaction Model

机译：琥珀酸中3Fe-4S（S-3）簇的电子自旋晶格弛豫测量：反硝化副球菌的泛醌还原酶。基于偶极-偶极相互作用模型的详细分析

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The electron spin-lattice relaxation for the 3Fe-4S (S-3) center in succinate:ubiquinone reductase has been examined using both inversion recovery and "picket-fence" pulse sequences at a temperature range of 4-8 K. The latter pulse sequence is used to eliminate the interference of spectral diffusion in frozen solids. An abnormally fast relaxation was observed for the S-3 center. We attribute this rapid relaxation to a magnetic dipolar interaction between the S-3 center and a nearby paramagnetic b-heme (cytochrome b). A model has been developed to treat the interaction between two paramagnetic redox centers in a rigid lattice at a fixed distance apart but with random orientations in a magnetic field. Both the contribution to the spin-lattice relaxation rate from the dipolar interaction (k_(1θ), which is anisotropic, and the intrinsic electron spin relaxation, which is scalar (k_(1scalar)), have been deduced. We find that the contribution of exchange interaction to the anisotropic part of the relaxation rate (k_(1θ)) is very small. Accordingly, we conclude that k_(1scalar) is dominated by the intrinsic electron spin-lattice relaxation. From k_(1θ), a lower limit (r > 10 A) has been deduced for the distance between the S-3 center and the b-heme.
机译：琥珀酸：泛醌还原酶中3Fe-4S（S-3）中心的电子自旋晶格弛豫已在4-8 K的温度范围内使用反转恢复和“栅栏”脉冲序列进行了检查。序列用于消除冻结固体中光谱扩散的干扰。观察到S-3中心异常快速松弛。我们将此快速松弛归因于S-3中心与附近的顺磁性b-血红素（细胞色素b）之间的磁偶极相互作用。已经开发出一种模型来处理刚性晶格中两个顺磁性氧化还原中心之间的相互作用，该相互作用以固定的距离但在磁场中具有随机方向。推论了偶极相互作用（k_（1θ），是各向异性的）和本征电子自旋弛豫，是标量的（k_（1scalar））对自旋晶格弛豫速率的贡献。交换相互作用对弛豫率（k_（1θ））的各向异性部分的影响很小，因此，我们得出结论，k_（1scalar）由本征电子自旋晶格弛豫控制，从k_（1θ）开始，下限推论出S-3中心与b-血红素之间的距离（r> 10 A）。

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