鉄-プロトポルフィリン-IXモデル化合物のヘムプロピオネートにおけるプロトン結合電子伝送反応
Jeffrey J Warren1, James M Mayer
1Beckman Institute, California Institute of Technology, MC 139-74, Pasadena, California 91125-0001, USA. jwarren@caltech.edu
Journal of the American Chemical Society
|April 29, 2011
まとめ
この研究では,ヘムプロピオネートが唯一の陽子部位として作用するヘムモデルシステムを開発しました. この研究は,ヘムプロピオネートを,ヘムタンパク質における陽子結合電子伝達反応の潜在的な活性部位として強調しています.
科学分野:
- バイオ・オーガニック化学 バイオ・オーガニック化学
- 生物物理化学 生物物理化学
- 化学物理 化学物理
背景:
- ヘムタンパク質は,生物学的酸化還元過程において重要な役割を果たします.
- 陽子結合電子伝送 (PCET) のメカニズムを理解することは,これらの生物学的機能を解読するために不可欠です.
- モデルシステムは,複雑な生物分子内の特定の化学現象を分離し,研究するために不可欠です.
研究 の 目的:
- ヘムプロピオネートが独占的な陽子ドナー/受容体となる簡素化されたヘムモデルシステムを開発する.
- このモデルシステムを含むプロトン結合電子伝送反応 (PCET) を調査する.
- ヘムタンパク質のPCET/CPET活性部位におけるヘムプロピオネートの潜在的な役割を評価する.
主な方法:
- プロトポルフィリンIX-モノメチルエステル (PPIX(MME)) とN-メチリミダゾール (MeIm) を利用してヘムモデルを作成しました.
- アセトニトリル溶媒でのPCET反応は,アスコルバート誘導体,TEMPOH,ヒドロキノン,TEMPO,ベンゾキノンなどの様々な還元および酸化剤を用いて試験された.
- 均衡定数,pK (a) とE (b) / 2の値が決定され,効果的結合解離自由エネルギー (BDFE) を計算する.
主要な成果:
- ヘムモデルシステム (PPIX ((MME)) Fe ((III)) ((MeIm)) ((2) -プロピオネート (Fe ((III) ~CO ((2)) をプロピオネートで唯一の陽子部位として成功裏に確立しました.
- Fe ((III) ~CO ((2)) と Fe ((II) ~CO ((2)) H形態の間の電子と陽子の移転によって媒介される可逆性還元反応が実証されています.
- Fe (II) ~CO (II) ~2) H. に対して,有効なBDFEを67.8 ± 0.6 kcal mol (-1) で計算した.
- 鉄の中心部での電子の移転と,遠隔のヘムプロピオネートでの陽子の移転を特定しました.
- TEMPOHとアスコルベート誘導体との反応における協調型陽子電子伝送 (CPET) 機構の証拠を提供した.
結論:
- ヘムプロピオネートは,PCET反応における重要な陽子転送部位として機能することができます.
- 開発されたヘムモデルシステムは,生物学的システムにおけるPCETの側面を効果的に模倣しています.
- ヘムプロピオネートは,PCET/CPETプロセスに関与するヘムタンパク質の活性部位における潜在的な重要な成分として認識されるべきである.
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