アデニンの低エネルギー非活性化チャネルの解読

Irene Conti¹, Marco Garavelli, Giorgio Orlandi

¹Dipartimento di Chimica G. Ciamician, Universita' di Bologna, Via F. Selmi, 2, 40126 Bologna, Italy.

Journal of the American Chemical Society

|October 23, 2009

まとめ

9H-アデニンの (1) L (a) 状態は超高速分解を誘発し,他の興奮状態は中間体として作用しない. N(9) -H光分裂は可能だが稀であるが,N(10) -H結合破裂は妨げられる.

科学分野:

フォトケミストリーフォトケミストリー
量子化学とは,量子化学である.
分子スペクトロスコピーは,分子スペクトロスコピーを用います.

背景:

アデニンは,核酸の基本的な成分です.
興奮状態のダイナミクスを理解することは,光生物学と光化学にとって極めて重要です.
無放射性崩壊経路は,興奮した分子の運命を左右する.

研究の目的:

9H-アデニンの最も低い興奮状態の無放射線分解経路をマッピングする.
観測された超高速ビプエポネンショナルの崩壊の背後にあるメカニズムを解明する.
潜在的な光分裂経路を調査するために.

主な方法:

CASPT2//CASSCFレベルの理論を用いた計算化学.
興奮状態のための最小エネルギー経路 (MEP) のマッピング.
円形の交差点 (CI) と潜在エネルギー表面の分析.

主要な成果:

5 eV未満の強い吸収を伴う (1) L (a) 状態は,パッカリング座標に沿って単調に崩壊し,S ((0)) / ((1) L (a) 円交差点になる.
(1) npi* と (1) L(b) 状態は最小値までリラックスし,基底状態 (S(0) で CIs に到達するにはエネルギーが必要です.
(1) L (a) 状態だけでは,観測された比率的な衰退を説明し,他の状態は有意な中間状態ではない.

結論:

(1) L (a) 状態は,9H-アデニンの超高速分解の主要な原動力である.
N(9) -H光分裂は, (1) L(a) から (1) pisigma(N9H) *への内部変換後に起こり得るが,量子産量は低い.
N10-H結合の光分裂は, (1) ピシグマ (N10H) *状態で高いバリアがあるため,エネルギー的に不利です.

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