水素原子抽象化のためのμ-オクソ二銅複合体の熱力学
Ghazanfar Ali1, Peter E VanNatta1, David A Ramirez1
1Department of Chemistry, University of Utah , Salt Lake City, Utah 84112-0850, United States.
Journal of the American Chemical Society
|December 7, 2017
まとめ
銅複合体は反転可能な脱プロトン化を経て,陽子-電子の移転に適した基本種を形成する. この研究は,メタンモノキシゲネーゼ酵素に関連する銅酸素種に関する洞察を示しています.
科学分野:
- バイオ有機化学
- 有機金属化学
- 酵素メカニズム
背景:
- 銅依存メタンモノキシゲナーゼ (MMO) 酵素はメタンの酸化に不可欠である.
- 銅と酸素の反応性を理解することは,MMOメカニズムを解明する鍵です.
- モノ-μ-ヒドロキソ複合体 {[Cu(tmpa) ]2-(μ-OH) }3+ (1) はモデルシステムとして用いられる.
研究 の 目的:
- 銅-バイ (μ-ヒドロキソ) 複合体のデプロトネーションを調査する.
- 銅-オクソの種とその反応性を特徴づける.
- [Cu2O]2+の熱力学的活性をメタン一酸化酵素の文脈で評価する.
主な方法:
- 低温 (−30°C) で複合体1の反転性脱プロトン化
- デプロトン化種のスペクトル学および電気化学的特徴付け (2).
- 結合解離自由エネルギー (BDFE) の測定を含む動力学的および熱力学的分析
- 密度関数理論 (DFT) の計算は,実験データに対して校正された.
主要な成果:
- 複合体1は,pKaが24.3である基礎種{[Cu(tmpa) ]2-(μ-O) }2+ (2) を形成するために逆転的にデプロトン化します.
- 種2はTEMPOHから 協調した陽子電子移転が可能である.
- 種2は77.2 kcal/molのBDFE ((OH)) を有する貧弱な水素原子抽出物である.
- [Cu2O]2+コアは,銅に依存したメタンモノキシゲナーゼ酵素において熱力学的に有効であることをDFT計算が示唆している.
結論:
- 特徴づけられた銅-オクソ種は,水素原子抽出と比較して異なった反応性を示す.
- この発見は,銅に依存したメタンモノキシゲナーゼ酵素の機能に関する重要な仕組みの洞察を提供します.
- この研究は,酵素によるメタンの酸化における[Cu2O]2+種の熱力学的実現可能性を支持する.
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