Huynh B H, Münck E, Orme-Johnson W H
Biochim Biophys Acta. 1979 Jan 25;576(1):192-203. doi: 10.1016/0005-2795(79)90497-5.
We have studied the MoFe protein from Azotobacter vinelandii OP with Mössbauer spectroscopy in applied magnetic fields up to 50 kG. The results are as follows. (1) The Mössbauer spectra of the S = 3/2 centers, which reside on the cofactor of nitrogenase, have been decomposed into six subcomponents. This suggests that each center contains 5-7, most probably 6, Fe atoms, thus confirming our earlier conclusions which were based on the quantitation of EPR data and on the assumption that the MoFe protein contains (30 +/- 2) Fe atoms. (2) Analysis of the high-field data shows that three subsites are characterized by a positive magnetic hyperfine coupling constant, A0, while A0 is negative for the other three sites. This observation demonstrates that the S = 3/2 centers are spin-coupled structures. (3) The zero-field splitting parameter D = +(6 +/- 1.5) cm-1 obtained from the Mössbauer data is in good agreement with our earlier EPR results, D approximately +5.5 cm-1. (4) The resolution of the Mössbauer spectra of the MoFe protein can be dramatically increased by employing Fourier transform deconvolution techniques. This allows a clear demonstration of spectral component S.
我们利用穆斯堡尔光谱对高达50 kG的外加磁场中的棕色固氮菌OP的钼铁蛋白进行了研究。结果如下：(1) 位于固氮酶辅因子上的S = 3/2中心的穆斯堡尔谱已被分解为六个子分量。这表明每个中心含有5 - 7个，很可能是6个铁原子，从而证实了我们早期基于EPR数据定量以及钼铁蛋白含有(30 ± 2)个铁原子这一假设得出的结论。(2) 高场数据分析表明，三个亚位点的特征是具有正的磁超精细耦合常数A0，而另外三个位点的A0为负。这一观察结果表明S = 3/2中心是自旋耦合结构。(3) 从穆斯堡尔数据获得的零场分裂参数D = +(6 ± 1.5) cm-1与我们早期的EPR结果D ≈ +5.5 cm-1非常吻合。(4) 通过采用傅里叶变换去卷积技术，钼铁蛋白的穆斯堡尔谱分辨率可显著提高。这使得能够清晰地展示光谱分量S。
