The electronic structure of Fe2+ in reaction centers from Rhodopseudomonas sphaeroides. I. Static magnetization measurements.
The electronic structure of Fe2+ in reaction centers from Rhodopseudomonas sphaeroides. I. Static magnetization measurements.
复制标题
球形红假单胞菌反应中心 Fe2 的电子结构。
DOI：
10.1016/s0006-3495(80)85030-2
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发表时间：
1980
影响因子：
3.4
通讯作者：
Feher,G
中科院分区：
文献类型：
--
作者：
Butler,WF;Johnston,DC;Shore,HB;Fredkin,DR;Okamura,MY;Feher,G
我们已经测量了静态磁化的未还原和还原反应中心，其醌含量不同。测量是在温度范围0.7度K小于T小于200度K和磁场高达10千克。电子g值，晶体场参数D，E，和交换相互作用，J，醌自旋和Fe 2+之间的确定使用自旋哈密顿形式主义。还原和未还原样品的有效磁矩μ eff/Fe 2+被确定为5.35 +/- 0.15玻尔磁子。这表明，与以前的研究结果一致，当反应中心被还原时，Fe 2+不会改变其价态。D全等为+5 cm-1和E/D全等为0.27的典型值与Fe处于具有菱形畸变的八面体环境中一致。对于具有一个和两个醌的反应中心，D和E的值大致相同。这些发现意味着醌最有可能不是Fe的配体。在还原反应中心的醌上的Fe 2+和自旋被发现与交换相互作用0小于/J/小于1 cm-1耦合。用轨道哈密顿量计算了S=2，L=2流形的25个态的能级，并将最低5个态的磁化强度与自旋哈密顿量的结果进行了比较，从而验证了自旋哈密顿量的有效性.利用轨道哈密顿量，我们计算出第一激发五重态的位置是340 cm-1以上的基态五重态。这是在很好的协议，由穆斯堡尔谱确定的四极分裂的温度依赖性。
We have measured the static magnetization of unreduced and reduced reaction centers that vary in their quinone content. Measurements were performed in the temperature range 0.7 degrees K less than T less than 200 degrees K and magnetic fields of up to 10 kG. The electronic g-value, crystal field parameters D, E, and the exchange interaction, J, between the quinone spin and Fe2+ were determined using the spin Hamiltonian formalism. The effective moment mu eff/Fe2+ of both reduced and unreduced samples were determined to be 5.35 +/- 0.15 Bohr magnetons. This shows, in agreement with previous findings, that Fe2+ does not change its valence state when the reaction centers are reduced. Typical values of D congruent to +5 cm-1 and E/D congruent to 0.27 are consistent with Fe being in an octahedral environment with rhombic distortion. The values of D and E were approximately the same for reaction centers having one and two quinones. These findings imply that quinone is most likely not a ligand of Fe. The Fe2+ and the spin on the quinone in reduced reaction centers were found to be coupled with an exchange interaction 0 less than /J/ less than 1 cm-1. The validity of the spin Hamiltonian was checked by using an orbital Hamiltonian to calculate energy levels of the 25 states of the S=2, L=2 manifold and comparing the magnetization of the lowest five states with those obtained from the spin Hamiltonian. Using the orbital Hamiltonian, we calculated the position of the first excited quintet state to be 340 cm-1 above the ground state quintet. This is in good agreement with the temperature dependence of the quadrupole splitting as determined by Mossbauer spectroscopy.