ガス状のm-アミノベンゾ酸の水分化:イオン対中性水素結合と水橋
Terrence M Chang1, Satrajit Chakrabarty, Evan R Williams
1Department of Chemistry, University of California , Berkeley, California 94720-1460, United States.
Journal of the American Chemical Society
|June 28, 2014
まとめ
水分子は,m-アミノベンゾ酸のクラスターで,カルボキシル酸よりも,陽子化されたアミンを好ましく水分化します. カーボキシル酸への水素結合は,水分が増えると起こり,同位体安定性と解離障壁に影響を及ぼします.
科学分野:
- 物理化学 物理化学
- 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.
- コンピューティング・ケミストリー
背景:
- 生物分子の水分化を理解することは,生物学的プロセスにとって極めて重要です.
- 陽子化されたアミノ酸は,充電された,中性的な機能群によって,複雑な水分化課題を提示します.
- 陽子化されたm-アミノベンゾ酸 (MABAH (((+)) との水の相互作用の研究は,基本的な水分化のメカニズムについての洞察を提供します.
研究 の 目的:
- MABAH (((+)) の中性カルボキシル酸群と陽子化されたアミン群の水分化を調査する.
- 水-MABAH (((+)) クラスタの構造的好みとエネルギー差を決定する.
- 水-バイオ分子相互作用の理論モデルのための基準を確立する.
主な方法:
- クラスター構造を調査するための赤外線光解離スペクトロスコーピー.
- アイソメア集団とエネルギーバリアを測定するためのレーザー誘発解離運動.
- エネルギーと構造を計算するための計算化学 (B3LYP/6-31+G**とMP2/6-31+G**)
主要な成果:
- 水は当初,小さなMABAH (((+) · (((H2O)) 1-5クラスターのカルボキシル酸陽子と結合しない.
- MABAH ((+) · ((H2O) 6) 以上の場合,水は炭酸陽子と水素結合し,安定した同位体を形成する.
- 水素結合イソマーはエネルギー的に優れている (エネルギーが≥0.5kJmol−1) で,特定の条件下では集団の>74%を占める.
結論:
- 水分化は,カルボキシル酸との有意な相互作用の前に,優先的にプロトン化されたアミン部位で発生します.
- 機能群間の水の橋渡しは,同位体安定性と解離経路に影響を与える.
- 実験的および計算的結果は,理論的な水分化モデルの厳格な基準を提供します.
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