ビス (μ-oxo) 二銅酵素における水素伝導に対する大規模なトンネル効果:理論的な研究
Kisoo Park1, Youngshang Pak, Yongho Kim
1Department of Applied Chemistry, Kyung Hee University, 1 Seochun-Dong, Giheung-Gu, Yongin-Si, Gyeonggi-Do 446-701, Korea.
Journal of the American Chemical Society
|January 27, 2012
まとめ
量子計算は,二銅酵素モデルにおける動的同位体効果を正確に予測し,C-H結合の活性化中に重要な水素トンネリングを明らかにします. このトンネリングは,効率的な水素転送機構を強調して,最小エネルギー経路と大きく異なる.
科学分野:
- バイオケミストリー バイオケミストリー
- コンピューティング・ケミストリー
- 酵素学 酵素学とは
背景:
- タイプIIIの銅酵素は,分子酸素を用いたアリファティックC-H結合の活性化に不可欠な二銅中心を特徴としています.
- ディコッパー酵素モデルは,水素移転において大きな運動同位体効果 (KIEs) を表しており,重要な量子トンネリングを示唆しています.
研究 の 目的:
- 変数移行状態理論を用いた二銅酵素モデルのKIEsとアーレニウスパラメータを正確に予測する.
- これらのシステム内の水素転送における多次元トンネリングの役割と効率を調査する.
主な方法:
- 最小エネルギー経路 (MEP) を決定するために,変数移行状態理論と量子力学計算を使用した.
- bis (μ-oxo) 二銅酵素の70原子の計算モデルを利用し,204次元の潜在エネルギー表面を定義した.
- 計算されたKIEsとArrheniusパラメータは,233Kのイソプロピルリガンド系に対して.
主要な成果:
- E (a) (H) - E (a) (D),A (H) /A (D),およびKIE (28.1で233K) の計算値と実験値との間で優れた一致を達成しました.
- 代表的なトンネリング経路 (RTP) 沿いのエネルギー最大値を下回る3.3kcal/molで0.54 Åの水素トンネルを特定しました.
- RTPがMEPから著しく逸脱し,重原子が水素トンネリングの前に移動することを示した.
結論:
- 変数移行状態理論は,二銅酵素モデルにおけるKIEsとArrheniusパラメータを正確にモデル化しています.
- 量子トンネリングは,古典的な反応経路とは異なり,水素の転送において非常に効率的な役割を果たします.
- この発見は,銅を含む酵素によるC-H結合活性化のメカニズムに関する重要な洞察を提供します.
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