Levy A, Kuppusamy P, Rifkind J M
Laboratory of Cellular and Molecular Biology, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224.
Biochemistry. 1990 Oct 9;29(40):9311-6. doi: 10.1021/bi00492a002.
Electron paramagnetic resonance spectra of methemoglobin reveal that, in addition to the major tetragonal high-spin aqueous complex and the low-spin hydroxide complex, three other complexes associated with the interaction of the distal histidine are resolved. These are a rhombic high-spin and two classes of low-spin bis-histidine complexes. By freeze-quenching experiments it is shown that the rhombic high-spin and one of the low-spin bis-histidine complexes (B) are at equilibrium with the dominant species. Incubation in the 210-260 K temperature range shifts the total equilibrium toward a low-energy state with the distal histidine coordinated to the iron (complex C).
高铁血红蛋白的电子顺磁共振光谱显示，除了主要的四方高自旋水合络合物和低自旋氢氧化物络合物外，还分辨出与远端组氨酸相互作用相关的另外三种络合物。它们是菱形高自旋和两类低自旋双组氨酸络合物。通过冷冻猝灭实验表明，菱形高自旋和一种低自旋双组氨酸络合物（B）与主要物种处于平衡状态。在210 - 260 K温度范围内孵育会使总平衡向低能态移动，此时远端组氨酸与铁配位（络合物C）。
