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トリプトファンのプロトン結合電子移転: プロトン受容体として水を使用した協調的なメカニズム

Ming-Tian Zhang¹, Leif Hammarström

¹Department of Photochemistry and Molecular Science, Uppsala University, Box 523, SE-751 20 Uppsala, Sweden.

Journal of the American Chemical Society

|April 20, 2011

まとめ

アミノ酸のプロトン結合電子伝送 (PCET) は,段階的または協調的なメカニズムによって発生することができます. この研究は,水による協調電子-陽子伝送 (CEP) が一般的な特徴であり,以前の理論モデルに挑戦していることを明らかにしています.

科学分野:

化学動力学化学動力学
バイオ物理化学バイオ物理化学
フォトケミストリーフォトケミストリー

背景:

陽子結合電子伝送 (PCET) 機構,特にpH依存性は,酵素とモデルにおけるチロシンについて議論されています.
PCETを理解することは,電子と陽子の移転を含む生物学的および合成システムにとって非常に重要です.

研究の目的:

[Ru(bpy) ((3))) ((2+) 単位と結びついたトリプトファン誘導体の分子内酸化運動を研究する.
陽子受容体として水を用いた電子移転のメカニズムとpH依存度を決定する.
実験結果と既存のPCETの理論モデルを比較する.

主な方法:

酸化運動を研究するために,レーザーフラッシュ消し法が採用されました.
反応経路の差異化のために,動的同位体効果を測定した.
反応速度のpH依存度を体系的に分析した.

主要な成果:

トリプトファンの酸化は,段階的な電子-陽子伝送 (ETPT) と協調された電子-陽子伝送 (CEP) の両方を介して行われます.
CEP経路は,pHに依存する速度と,ETPTよりも高い運動同位体効果を示しています.
観測されたCEP pH依存性は,水が陽子受容体としてトリプトファンの理論的予測と矛盾しています.

結論:

陽子受容体としての水による協調的な電子-陽子移転 (CEP) は,アミノ酸酸化における一般的なメカニズムである.
これらの発見は,CEPがこれらの条件下でETPTと競争できないと予測する現在の理論モデルに異議を唱える.
この研究は,PCETプロセスの詳細な理解をサポートする実験的証拠を提供します.

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