Significant Change in Electronic Structures of Heme Upon Reduction by Strong Coulomb Repulsion between Fe d Electrons
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- 作者：Katsumasa Kamiya ; Shuji Yamamoto ; Kenji Shiraishi ; Atsushi Oshiyama
- 刊名：Journal of Physical Chemistry B
- 出版年：2009
- 出版时间：May 14, 2009
- 年：2009
- 卷：113
- 期：19
- 页码：6866-6872
- 全文大小：251K
- 年卷期：v.113,no.19(May 14, 2009)
- ISSN：1520-5207
文摘
We report total-energy electronic-structure calculations based on the density functional theory performed on a low-spin heme. We have found that the high-lying occupied and low-lying unoccupied states having Fe d and/or porphyrin π orbital character are significantly rearranged upon the reduction of the heme. An analysis of these states shows that the remarkable elevation of the Fe d levels takes place due to the strong Coulombic repulsion between accommodated d electrons. Due to a peculiarity of the heme, this elevation could be controlled by lower-lying empty porphyrin π states, leading to electron transfer from Fe d orbitals to the porphyrin π ones in order to reduce the Coulomb-energy cost. This self-limiting mechanism provides a natural explanation not only for the present calculated results, but also for general electron delocalization appearing under various physiological conditions, regardless of the types of the hemes.