Center for Quantum Science and Technology under Extreme Conditions (KYOKUGEN), Osaka University, Toyonaka, Osaka, Japan.
J Inorg Biochem. 2011 Dec;105(12):1596-602. doi: 10.1016/j.jinorgbio.2011.09.007. Epub 2011 Sep 10.
The low-lying electronic states of the ferrous high-spin heme in deoxy-myoglobin (deoxy-Mb) and deoxy-hemoglobin (deoxy-Hb) were probed by multi-frequency electron paramagnetic resonance (MFEPR) spectroscopy. An unexpected broad EPR signal was measured at the zero magnetic field using cavity resonators at 34-122 GHz that could not be simulated using any parameter sets for the S=2 spin Hamiltonian assuming spin quintet states in the (5)B(2) ground state. Furthermore, we have observed novel, broad EPR signals measured at 70-220 GHz and 1.5K using a single pass transmission probe. These signals are attributed to the ferrous high-spin heme in deoxy-Mb and deoxy-Hb. The resonant peaks shifted to a higher magnetic field with increasing frequency. The energy level separation between the ground singlet and the first excited state at the zero magnetic field was directly estimated to be 3.5 cm(-1) for deoxy-Hb. For deoxy-Mb, the first two excited singlet states are separated by 3.3 cm(-1) and 6.5 cm(-1), respectively, from the ground state. The energy gap at the zero magnetic field is directly derived from our MFEPR for deoxy-Mb and deoxy-Hb and strongly supports the theoretical analyses based on the Mössbauer and magnetic circular dichroism experiments.
亚铁高自旋血红素在脱氧肌红蛋白（脱氧 Mb）和脱氧血红蛋白（脱氧 Hb）中的低能电子态通过多频电子顺磁共振（MFEPR）光谱进行了研究。在零磁场下，使用腔谐振器在 34-122 GHz 下测量到了一个意想不到的宽 EPR 信号，该信号无法使用任何 S=2 自旋哈密顿参数集来模拟，假设在（5）B（2）基态中存在自旋 quintet 态。此外，我们还观察到了在 70-220 GHz 和 1.5K 下使用单通传输探头测量到的新型宽 EPR 信号。这些信号归因于脱氧 Mb 和脱氧 Hb 中的亚铁高自旋血红素。随着频率的增加，共振峰向更高的磁场移动。在零磁场下，基态单重态和第一激发态之间的能级分离直接估计为 3.5 cm(-1)，用于脱氧 Hb。对于脱氧 Mb，第一和第二激发单重态分别与基态分离 3.3 cm(-1)和 6.5 cm(-1)。零磁场的能隙直接来自我们对脱氧 Mb 和脱氧 Hb 的 MFEPR，强烈支持基于穆斯堡尔和磁圆二色实验的理论分析。
