Rawlings J, Stephens P J, Nafie L A, Kamen M D
Biochemistry. 1977 Apr 19;16(8):1725-9. doi: 10.1021/bi00627a032.
The near-infrared magnetic circular dichroism (MCD) of Rhodospirillum rubrum, Chromatium vinosum, and Rhodopseudomonas palustris cytochromes c' are reported. The spectra of the reduced protein are very similar to those of deoxymyoglobin. The spectra of the oxidized proteins in the pD range 1-13 can be analyzed on the basis of four species A, B, C, and D. The existence of nine species, reported in a recent electron paramagnetic resonance study, is not substantiated. The MCD spectra support the assignment of B as high spin and C and D as low spin. The MCD of species A is close to that of high-spin proteins and does not support the recently proposed assignment of a mixed high- and intermediate-spin ground state for this species. The energies of the near-IR electronic transitions of all four oxidized species point to axial ligation via oxygen, assuming histidine to be the opposite axial ligand. Unfortunately, insufficient model compounds with ligation by carboxyl or hydroxyl moieties exist to enable more precise assignments.
报道了红螺菌、嗜酒色杆菌和沼泽红假单胞菌细胞色素c'的近红外磁圆二色性（MCD）。还原态蛋白质的光谱与脱氧肌红蛋白的光谱非常相似。在pD范围为1 - 13时，氧化态蛋白质的光谱可基于四种状态A、B、C和D进行分析。最近一项电子顺磁共振研究报道的九种状态的存在未得到证实。MCD光谱支持将B指定为高自旋，C和D指定为低自旋。状态A的MCD接近高自旋蛋白质的MCD，不支持最近提出的该状态具有混合高自旋和中间自旋基态的指定。假设组氨酸为相反的轴向配体，所有四种氧化态物质的近红外电子跃迁能量表明通过氧进行轴向配位。不幸的是，存在的通过羧基或羟基部分进行配位的模型化合物不足，无法进行更精确的指定。
