非ヘム・チオラート・リガート・コバルト・スーペロキソ・コンプレックス:合成とスペクトロスコピカルな特徴付け,計算的研究,そして水素原子抽象反応性
Jesse B Gordon1, Avery C Vilbert2, Maxime A Siegler1
1Department of Chemistry , The Johns Hopkins University , 3400 North Charles Street , Baltimore , Maryland 21218 , United States.
Journal of the American Chemical Society
|February 19, 2019
まとめ
新しいコバルト-スーパーオクソ複合体が合成され研究された. この複合体は,提案された酵素とは異なり,硫黄ドナーを酸素化する代わりに,O-H結合から水素原子を抽出し,メタロ酵素の選択性についての洞察を提供します.
科学分野:
- 無機化学
- バイオ有機化学
- 有機金属化学
背景:
- 非ヘムチオール酸化酵素は,S-酸化チオラートドナーを介した金属-スーペロキソ介質を介してO2を活性化することを提案しています.
- このような中間物質の反応性を理解することは,生物学的酸素活性化メカニズムの解明に不可欠です.
研究 の 目的:
- 希少なチオラート結合コバルト-スーパーオクソ複合体を合成し,特徴づけること.
- 硫黄ドナーとO-H結合に対するこの複合体の反応性を調査する.
- 非ヘムチオール酸化酵素で提案されたメカニズムとの反応性を比較する.
主な方法:
- コバルト (II) ディチオラト複合体の合成と特徴付け
- O2と反応してコバルト-スーパーオックス種を形成する.
- スペクトロスコープ (共振ラーマン,EPR,X線吸収) と構造的特徴.
- 密度関数理論 (DFT) の計算
- O-H結合の酸化と陽子結合の電子移転を含む反応性研究.
主要な成果:
- 希少なチオラート結合コバルト-スーペロキソ複合体Co ((O2) ((Me3TACN)) ((S2SiMe2) が成功して生成され,特徴づけられました.
- 複合体は,分子内または外的硫黄ドナーにS-酸素を供給しなかった.
- 複合体は,H原子抽象によってO-H結合を効果的に酸化し,結合解離自由エネルギー (BDFE) の限界は≤70 kcalmol-1である.
- DFTの計算は観測された反応性を支持し,推定のCOOH製品のBDFEが67 kcalmol-1であると予測した.
結論:
- チオラート結合コバルト-スーペロキソ種は,S-酸素化よりもH原子抽出を好む選択性を示す.
- この発見は,酸素活性化に関与する非ヘム金属酵素のメカニズムに関する重要な洞察を提供します.
- この研究は,金属酵素の機能において,H原子抽象化などの代替反応モードを考慮する重要性を強調している.
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