Eglinton D G, Gadsby P M, Sievers G, Peterson J, Thomson A J
Biochim Biophys Acta. 1983 Feb 15;742(3):648-58. doi: 10.1016/0167-4838(83)90284-4.
The magnetic circular dichroism (MCD) spectra of three horse heart metmyoglobin compounds, the cyanide, azide and hydroxide forms, have been measured in the visible and near infrared spectral regions at temperatures down to 1.5 K. The three compounds are all virtually completely low-spin at low temperatures with ground g factors of decreasing rhombicity in the order CN- greater than N3- greater than OH-. The MCD magnetization curves have been constructed at selected wavelengths throughout the visible and near infrared regions. The curves are independent of wavelength, showing that all the bands studied are x,y polarized and can, moreover, be satisfactorily fitted to the g factors determined by EPR spectroscopy with theoretical expressions (Thomson, A.J. and Johnson, M.K. (1980) Biochem. J. 191, 411-420). This confirms the assignment and polarizations of the near infrared region low-spin ferric haem charge-transfer bands. The energies of these transitions are markedly dependent upon the added axial ligand, ranging from 1595 to 1295, and 1050 nm for the compounds CN-, N3- and OH-. The MCD spectra of bovine liver catalase and its cyanide adduct have been recorded in the Soret, visible and near infrared regions. Catalase is know to have phenolate anion as the proximal ligand of the haem group. The forms of the spectra make an interesting comparison with those of the analogous metmyoglobin derivatives, in which histidine is the proximal ligand. The MCD spectra of catalase at 4.2 K is an example of a fully high-spin haemoprotein. The cyanide compound is completely low-spin at 4.2 K. The near infrared charge-transfer band is at 1300 nm, showing the effect on the energy of this band of changing from imidazole to phenolate ion as the proximal ligand to haem.
已在低至1.5 K的温度下，于可见光和近红外光谱区域测量了三种马心高铁肌红蛋白化合物（氰化物、叠氮化物和氢氧化物形式）的磁圆二色性（MCD）光谱。这三种化合物在低温下实际上都几乎完全处于低自旋状态，其基态g因子的菱形度按CN-＞N3-＞OH-的顺序降低。已在整个可见光和近红外区域的选定波长处构建了MCD磁化曲线。这些曲线与波长无关，表明所研究的所有谱带都是x、y偏振的，而且可以用理论表达式（汤姆森，A.J.和约翰逊，M.K.（1980年）《生物化学杂志》191卷，411 - 420页）将其令人满意地拟合到由电子顺磁共振光谱法测定的g因子上。这证实了近红外区域低自旋铁血红素电荷转移谱带的归属和偏振情况。这些跃迁的能量明显取决于所添加的轴向配体，对于CN-、N3-和OH-化合物，其范围分别为1595、1295和1050 nm。已在索雷特带、可见光和近红外区域记录了牛肝过氧化氢酶及其氰化物加合物的MCD光谱。已知过氧化氢酶以酚盐阴离子作为血红素基团的近端配体。这些光谱的形式与以组氨酸作为近端配体的类似高铁肌红蛋白衍生物的光谱形成了有趣的对比。4.2 K时过氧化氢酶的MCD光谱是完全高自旋血红素蛋白的一个例子。氰化物化合物在4.2 K时完全处于低自旋状态。近红外电荷转移谱带位于1300 nm处，显示了从咪唑作为血红素的近端配体转变为酚盐离子对该谱带能量的影响。
