González Pablo J, Barrera Guillermo I, Rizzi Alberto C, Moura José J G, Passeggi Mario C G, Brondino Carlos D
REQUIMTE, Departamento de Quimica, Centro de Quimica Fina e Biotecnologia, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
J Inorg Biochem. 2009 Oct;103(10):1342-6. doi: 10.1016/j.jinorgbio.2009.06.006. Epub 2009 Jun 27.
Electron transfer proteins and redox enzymes containing paramagnetic redox centers with different relaxation rates are widespread in nature. Despite both the long distances and chemical paths connecting these centers, they can present weak magnetic couplings produced by spin-spin interactions such as dipolar and isotropic exchange. We present here a theoretical model based on the Bloch-Wangsness-Redfield theory to analyze the dependence with temperature of EPR spectra of interacting pairs of spin 1/2 centers having different relaxation rates, as is the case of the molybdenum-containing enzyme aldehyde oxidoreductase from Desulfovibrio gigas. We analyze the changes of the EPR spectra of the slow relaxing center (Mo(V)) induced by the faster relaxing center (FeS center). At high temperatures, when the relaxation time T(1) of the fast relaxing center is very short, the magnetic coupling between centers is averaged to zero. Conversely, at low temperatures when T(1) is longer, no modulation of the coupling between metal centers can be detected.
含有具有不同弛豫速率的顺磁性氧化还原中心的电子转移蛋白和氧化还原酶在自然界中广泛存在。尽管连接这些中心的距离和化学路径都很长，但它们可以呈现出由自旋 - 自旋相互作用（如偶极和各向同性交换）产生的弱磁耦合。我们在此提出一个基于布洛赫 - 王斯尼斯 - 雷德菲尔德理论的理论模型，以分析具有不同弛豫速率的自旋1/2中心相互作用对的电子顺磁共振（EPR）谱对温度的依赖性，例如来自巨大脱硫弧菌的含钼酶醛氧化还原酶的情况。我们分析了快速弛豫中心（FeS中心）对缓慢弛豫中心（Mo(V)）的EPR谱的影响。在高温下，当快速弛豫中心的弛豫时间T(1)非常短时，中心之间的磁耦合平均为零。相反，在低温下当T(1)较长时，无法检测到金属中心之间耦合的调制。
