合成ヘム・銅複合体における光誘導による一酸化炭素の移動
H Christopher Fry1, Andrew D Cohen, John P Toscano
1Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
Journal of the American Chemical Society
|April 28, 2005
まとめ
合成ヘム・銅複合体の光解離した一酸化炭素 (CO) は,銅に素早く結合し,ヘムに戻ります. このCO転送メカニズムは,シトクロームc酸化酵素の活性部位を模倣する.
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
- フォトケミストリー フォトケミストリー
- スペクトロスコーピーは,スペクトロスコーピーを用います.
背景:
- ヘム-銅複合体は,生物系,特にサイトクロームc酸化酵素において,ガス輸送および酸化還元反応において極めて重要です.
- 炭素一酸化物 (CO) の結合と放出などのリガンドダイナミクスを理解することは,酵素メカニズムを明らかにする鍵です.
- 合成モデルは,複雑な生物学的活性部位の機能的メカニズムについての洞察を提供します.
研究 の 目的:
- 合成ヘム-CO/銅複合体における一酸化炭素 (CO) の解離と転移のダイナミクスを調査する.
- 合成複合体のCO伝達機構と,シトクロームc酸化酵素のヘム (a3) /Cu (b) 活性部位を比較する.
- ヘムと銅の分子の間のCO伝送を制御する運動および熱力学的パラメータを決定する.
主な方法:
- COの解離と結合を監視するための時間解像度赤外線 (TRIR) スペクトロスコーピー.
- CO移転中にソレート帯を追跡するために,トランジント吸収 (TA) UV-VISスペクトロスコーピーを用いる.
- アクティベーションエンタルピーを計算するために,温度に依存する運動データのイーリング分析.
主要な成果:
- 合成ヘム-CO/銅複合体, [((6) L) Fe (((II) (((CO)..Cu ((I) ] (((+) から COの効率的な解離が観察されました.
- 光解離したCOは,速度常数 k(1) = 1.5 x 10(5) s(-1) で,銅中心に一時的に結合する.
- その後,銅からヘムに戻るCOの転送は速度定数 k(2) = 1600 s(-1で発生し,アクティベーションエンタルピーは 43.9 kJ mol(-1) でした.
結論:
- この研究では,シトクロームc酸化酵素と同様の,一時的な銅結合を含む2段階のCO転送メカニズムが明らかになりました.
- 銅からのCO解離は,合成複合体のヘムに結合する小分子を調節するようです.
- この発見は,合成システムと生物学的システムの両方に関連するヘム-銅の活性部位に関する貴重な力学的な洞察を提供します.
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