Fe-only hydrogenaseのアクティブセンターに関する密度関数理論の研究: レドックス状態の特徴と電子構造
1School of Chemistry, The Queen's University of Belfast, Belfast, BT9 5AG, UK.
Journal of the American Chemical Society
|May 2, 2002
まとめ
密度関数理論の計算は,鉄のみの水酸化物の活性状態を明らかにする. 酸化され,活性状態はFe (II) -Fe (I) であるが,還元状態は陽子化されたFe (I) -Fe (I) 複合体であり,CO抑制パターンを説明する.
科学分野:
- バイオケミストリーとバイオ物理学
- コンピューティング・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
背景:
- 鉄のみの水酸化酵素は,生物学的水素代謝に不可欠な金属酵素である.
- 活性センターの酸化還元状態を理解することは,その触媒機構の解明の鍵です.
- 以前の研究では,さまざまなアクティブサイト構成が提案されていますが,実験的検証は依然として困難です.
研究 の 目的:
- 密度関数理論 (DFT) を用いて,鉄のみの水酸化物における活性センターの可能なリドックス状態を計算的に調査する.
- 計算された構造と振動周波数を実験データと相関させ,活性状態と非活性状態を特定する.
- これらの酵素の反応性とCO阻害を左右する電子構造と結合特性を分析する.
主な方法:
- 広範な密度関数理論 (DFT) の計算は,アクティブセンターを表すモデル複合体で実行されました.
- 潜在的な酸化還元状態の構造が最適化され,一酸化炭素 (CO) の伸縮周波数が計算されました.
- 計算された振動周波数と構造パラメータを,利用可能な実験データと比較した.
主要な成果:
- 完全に酸化され,不活性な状態は,遠端鉄 (Fe) の (Fe) d) にあるヒドロキシル基を持つFe (II) -Fe (II) 複合体として識別された.
- 酸化され,活性状態はFe (II) -Fe (I) 複合体であると決定され,以前の割り当てと一致しました.
- 完全に還元された状態は混合物として存在し,主に陽子化されたFe (I) -Fe (I) 複合体であり,Fe (II) -Fe (II) 水素成分が小さい.
- 外因的なCOはFe (II) -Fe (I) 状態に強く結合するが,Fe (I) -Fe (I) 状態には結合しないので,COの抑制が観察されたことを説明する.
- 境界軌道 (Fe e ((g) - 橋渡しCO 2 piミックス) は,不活性状態では空き,活性状態では半開き,還元状態では完全開きであるため,反応性にとって極めて重要です.
結論:
- DFT計算は,鉄のみのヒドロゲンゼ活性センターのリドックス状態と振動特性を正確にモデル化します.
- Fe (II) -Fe (I) 複合体とプロトン化Fe (I) -Fe (I) 複合体は,それぞれ酸化,活性,完全還元状態を表しています.
- Fe e ((g) -ブリッジングCO2pi境界軌道の電子構造は,CO抑制に対する酵素の反応性と反応を決定する.
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