陽子化されたトリグリシンの陽子移動とタウトメリズム
C F Rodriquez1, A Cunje, T Shoeib
1Department of Chemistry and Centre for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario, Canada M3J 1P3.
Journal of the American Chemical Society
|July 18, 2001
まとめ
陽子化されたグリチルグリチルグリシン (GGG) の陽子移動には,小さなエネルギー障壁が伴う. 最も安定したプロトネーション部位は,N端のカルボニル酸素であり,断片化経路に影響を与える.
科学分野:
- コンピューティング・ケミストリー
- 物理化学 物理化学
- バイオ物理化学 バイオ物理化学
背景:
- グリチルグリチルグリシン (GGG) は,生物学的に重要な三ペプチドです.
- プロトネーションと断片化の理解は,ペプチド化学にとって極めて重要です.
- GGGのプロトネーションに関する以前の研究は,さまざまな結果をもたらしました.
研究 の 目的:
- 陽子化されたグリシルグリシルグリシン (GGG) の陽子移動経路を調査する.
- エネルギーハイパー表面を特徴付け,臨界点を特定する.
- 最も有利なプロトネーション部位と断片化メカニズムを決定する.
主な方法:
- B3LYP/6-31++G ((d,p) レベルの理論を用いた密度関数理論 (DFT) の計算.
- GGGのエネルギーハイパー表面上の19の臨界点 (11の最小値,8のサドルポイント) の特徴.
- 陽子の移動と断片化のための移行状態構造と自由エネルギーの障壁の計算.
主要な成果:
- 11つの安定したプロトン化GGG同位体と8つの移行状態を特定しました.
- 最も有利なプロトネーション部位は,O-H.N水素結合によって安定したN端のカルボニル酸素である.
- b(2) イオン形成のための計算されたエネルギーバリアは32.5 kcal mol(-1) である.
- 計算された陽子の親和度および基礎度値は,改訂された実験データと非常に一致しています.
結論:
- 陽子化されたGGGにおける陽子移動は,小さな個々の自由エネルギー障壁によって特徴付けられます.
- N端のカルボニル酸素でのプロトネーションはエネルギー的に好ましいので,特定の断片化経路につながります.
- この研究は,GGG陽子の親和性と基本性に関する正確な計算データを提供し,実験結果と一致しています.
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