濃縮された酸化鉄血タンパク質とモデル化合物のスーパーオクソ鉄化状態である
Roman Davydov1, James D Satterlee, Hiroshi Fujii
1Department of Chemistry, Northwestern University, 2156 Sheridan Road, Evanston, Illinois 60208-3113, USA.
Journal of the American Chemical Society
|December 25, 2003
まとめ
オキシヘムの冷凍還元により,以前から想定されていた過酸化鉄体 ([FeO2]per7) 形態とは異なる超酸化鉄体 ([FeO2]sup7) 状態が生成されます. このスーパーオクソ・フェラー中介物質は,主要な還元産物であり,加熱するとペロクソ/ヒドロペロクソ・フェラー状態に変換されます.
科学分野:
- バイオケミストリー バイオケミストリー
- バイオ・オーガニック化学 バイオ・オーガニック化学
- スペクトロスコーピーは,スペクトロスコーピーを用います.
背景:
- 多くの研究が[FeO2]7センターをペロキソフェリック ([FeO2]per7) として特徴づけ,そこでフェリヘムはダイアニオン型ペロキソリガンドと結合する.
- このペロキソフェリック状態は, [FeO2]6の親体を,追加された電子がO-O部分に局所する超オキソフェリック中心として見れば,ヒューリスティック的に理解できます.
研究 の 目的:
- 様々なオキシヘム複合体の冷凍還元によって生成される[FeO2]7センターの性質を調査する.
- これらの還元されたオキシヘム中間物質の電子構造とスピン密度局所を決定する.
- 主要還元産物とその後の変換を明らかにする.
主な方法:
- 電子パラマグネティック共振 (EPR) と電子核二重共振 (ENDOR) の実験が行われました.
- 77Kでの冷凍還元は,減少したオキシヘム種を生成するために使用されました.
- モノメアオキシヘモグロビン (oxy-GMH3),酸化鉄性オクタエチルポルフィリン,およびヘムモデル (シクリデン) の研究が行われました.
主要な成果:
- EPR/ENDORの実験では,生成された[FeO2]7の中心は"超酸化鉄" ([FeO2]sup7) で,超酸化鉄ではないことが明らかになった.
- ほぼ単位のスピン密度が,低スピンの鉄イオンにコーディネートされたスーパーオクソ部分の端に局所化された.
- [FeO2]sup7種は,150K以上で回するとペロキソ/ヒドロペロキソ-フェリック ([FeO2H]7) 中間物質に変換される.
結論:
- オキシヘム冷凍還元の主な還元産物は,スーパーオキシ鉄 ([FeO2]sup7) 種である.
- ペロキソ/ヒドロペロキソ-フェリック状態への内部リドックス移行は,H結合と陽子提供のような環境要因の影響を受けます.
- これらの発見は,以前の特徴付けに異議を唱え,ヘム還元中介物質に関する新しい理解を提供します.
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