フォスフォトリエステルの水解:重原子同位体効果による並列反応における移行状態の決定
M A Anderson1, H Shim, F M Raushel
1Institute for Enzyme Research and the Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53705, USA.
Journal of the American Chemical Society
|September 20, 2001
まとめ
この研究では,O,O-ジエチルフォスフォリコルリンヨウ酸化物 (DEPC) とO,O-ジエチル-m-ニトロベンジル酸化物 (DEmNBP) のアルカリ性水解中に酸素-18同位体効果を測定しました. 大規模な一次および二次効果は,著しい圧縮による高度な関連性のある移行状態を示しています.
科学分野:
- 化学的運動学 化学的運動学
- イソトープ効果とは
- 反応メカニズム 反応機構
背景:
- オーガノフォスファートのアルカリ性水解は,生化学と環境科学において極めて重要です.
- 移行状態の構造を理解することは,反応経路の洞察を提供します.
- 酸素-18同位体の効果は,結合破裂と形成の程度を明らかにすることができます.
研究 の 目的:
- DEPCとDEmNBPのアルカリ性水解における第一および二次酸素-18同位体の効果を定量化するために.
- これらの水解反応の移行状態構造を調査する.
- 反応中の分子圧縮と同位体効果を相関させるため.
主な方法:
- イソトープ効果測定のリモートラベル法を使用した.
- 精密な重原子同位体効果の決定のために,同位体比質量スペクトロメトリーを使用しました.
- パラレル反応と不完全なラベリングの修正を適用しました.
主要な成果:
- DEPCは,主性 (18) Oイソトープ効果1.041 ± 0.003と,次性効果1.033 ± 0.002.2を示した.
- DEmNBPは1.052 ± 0.003.3のプライマリ (18) O同位体効果を示した.
- 両方の反応は大きな (18) O同位体効果をもたらした.
結論:
- 主要な第一および二次 (18) O同位体効果は,高度な関連性のある移行状態を示唆する.
- これらの発見は,重要な核愛者のアプローチと移行状態での分子圧縮を示しています.
- この結果は,水解の間に協調的な結合形成と断裂の有力な証拠を提供します.
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