Richards A J, Lowe D J, Richards R L, Thomson A J, Smith B E
School of Chemical Sciences, University of East Anglia, Norwich U.K.
Biochem J. 1994 Jan 15;297 ( Pt 2)(Pt 2):373-8. doi: 10.1042/bj2970373.
FeMoco, a low-M(r) metal cluster of probable composition Fe7MoS9 complexed with homocitrate, has been extracted with N-methylformamide from the MoFe protein of the nitrogenase enzyme from Klebsiella pneumoniae. The binding of cyanide and thiols to the FeMoco cluster in its paramagnetic S = 3/2 oxidation level has been studied by low-temperature e.p.r. and magnetic-circular-dichroism (m.c.d.) spectroscopies. Cyanide binds to isolated FeMoco at more than one site, and causes changes in the g values form g = 4.6, 3.2, 2.0 to g = 4.29, 3.82, 2.02 E.p.r. competition studies indicate that one cyanide can be displaced by thiolate from one type of site. The form of the low-temperature m.c.d. spectrum is little changed by ligand binding, thus the basic cluster structure remains intact. However, when benzenethiol is bound, a new intense band (lambda 387 nm) is observed, indicating the generation of an increased ligand-to-cluster charge-transfer interaction.
固氮铁钼辅因子（FeMoco）是一种低分子量的金属簇合物，其可能的组成为Fe₇MoS₉，并与高柠檬酸络合。它已用N-甲基甲酰胺从肺炎克雷伯氏菌固氮酶的钼铁蛋白中提取出来。通过低温电子顺磁共振（e.p.r.）和磁圆二色性（m.c.d.）光谱学研究了氰化物和硫醇在其顺磁S = 3/2氧化态下与FeMoco簇的结合情况。氰化物在多个位点与分离的FeMoco结合，并导致g值从g = 4.6、3.2、2.0变为g = 4.29、3.82、2.02。电子顺磁共振竞争研究表明，一种氰化物可以被硫醇盐从一种位点取代。配体结合对低温磁圆二色性光谱的形式影响很小，因此基本的簇结构保持完整。然而，当苯硫醇结合时，会观察到一个新的强吸收带（λ 387 nm），这表明配体到簇的电荷转移相互作用增强。
