Mawatari K, Matsukawa S, Yoneyama Y
Biochim Biophys Acta. 1983 Jun 29;745(3):219-28. doi: 10.1016/0167-4838(83)90053-5.
Absorption and circular dichroism (CD) spectra of the Soret band, assigned as a pi-pi transition of the porphyrin pi-electron system, showed a great difference between alpha and beta subunits in the ferric state (alpha +, beta +). The nonequivalence of the spectra between alpha + and beta + subunits partly originates from the difference in the strength of the bond between heme iron and the proximal histidine. The peak positions for absorption and CD spectra of the ferric derivatives associated with F-, H2O, N-3 and CN- of the isolated subunits qualitatively correlate with the spin state of the ferric heme. The Soret absorption spectra obtained by simple addition of those for alpha + and beta + subunits are very similar to those for methemoglobin A (metHb A). On the other hand, the arithmetic means for the Soret CD spectra of alpha + and beta + subunits are different from those for metHb A. These differences were not observed between the Soret CD spectra of alpha 1 beta 1 dimer, which is predominantly present in metHb Hirose (beta 37Trp-Ser), and those of tetrameric metHb A. Therefore, the interaction between alpha 1 and beta 1 subunits to make the alpha 1 beta 1 dimer may strongly affect the CD spectral properties of alpha + and beta + subunits. The effect of the interaction between two homogeneous dimers, alpha 1 beta 1 and alpha 2 beta 2, forming a tetramer, on the Soret CD spectral properties, if any, is very small compared with that between alpha 1 and beta 1 subunits.
作为卟啉π电子体系π-π跃迁的索雷特带的吸收光谱和圆二色性（CD）光谱显示，处于高铁状态（α+，β+）的α和β亚基之间存在很大差异。α+和β+亚基之间光谱的不等价部分源于血红素铁与近端组氨酸之间键强度的差异。与分离亚基的F-、H2O、N-3和CN-相关的高铁衍生物的吸收光谱和CD光谱的峰位与高铁血红素的自旋状态定性相关。通过简单叠加α+和β+亚基的光谱得到的索雷特吸收光谱与高铁血红蛋白A（metHb A）的光谱非常相似。另一方面，α+和β+亚基的索雷特CD光谱的算术平均值与metHb A的不同。在主要存在于广濑高铁血红蛋白（β37Trp-Ser）中的α1β1二聚体的索雷特CD光谱与四聚体metHb A的光谱之间未观察到这些差异。因此，α1和β1亚基之间相互作用形成α1β1二聚体可能会强烈影响α+和β+亚基的CD光谱特性。与α1和β1亚基之间的相互作用相比，形成四聚体的两个同质二聚体α1β1和α2β2之间的相互作用对索雷特CD光谱特性的影响（如果有的话）非常小。
