セレニウムK-エッジ高解像度X線吸収スペクトロスコーピーによって明らかにされた窒素酵素フェモコの局所電子構造

Justin T Henthorn¹, Renee J Arias², Sergey Koroidov³

¹Max Planck Institute for Chemical Energy Conversion , Stiftstr. 34-36 , D-45470 Mülheim an der Ruhr , Germany.

Journal of the American Chemical Society

|July 30, 2019

まとめ

研究者らは,窒素酵素のFeMoコファクターにセレニウム置換を用いて,その電子構造を調査した. これは不対称な電子分布を明らかにし,鉄と硫黄のクラスターに関する以前の仮定に異議を唱えた.

科学分野:

生物化学
バイオ物理学
材料科学

背景:

窒素酵素は,大気中の窒素をアンモニアに変換するのに不可欠な複雑な酵素です.
活性部位であるFeMoコファクター (FeMoco) の電子構造を理解することは極めて重要ですが,その複雑さのために困難です.
FeMocoで硫黄をセレニウムで選択的に置換することは,局所的な電子特性を研究するための新しい方法を提供します.

研究の目的:

セレニウム置換を用いたFeMoコファクターの電子構造を調査する.
高エネルギー解像度の光検出X線吸収光譜 (HERFD XAS) と拡張X線吸収微細構造 (EXAFS) を適用してFe-Se相互作用を検出する.
Mo依存ニトロゲンゼにおける基板結合における電子的および構造的変化を解明する.

主な方法:

FeMoコファクターにおける硫黄をセレニウムで選択的に置換する.
高エネルギー解像度光検出X線吸収スペクトロスコーピー (HERFD XAS)
拡張X線吸収微細構造 (EXAFS) 分析
時間依存密度関数理論 (TDDFT) の計算
小分子モデルの研究

主要な成果:

FeMocoでのセレニウム置換は,電子配送における有意な非対称性を明らかにした.
電子構造は,以前に鉄硫黄のクラスターで想定されていたよりも局所化している.
HERFD XASとEXAFSのデータは,Fe2/Fe6に対する反鉄磁気結合の差異性ペアの割り当てを支持している.
HERFD XASとEXAFSは,CO抑制されたMoFeタンパク質の基板結合時の電子的および構造的変化を成功裏に検出しました.

結論:

セレニウム置換は,FeMo共因子の局所電子構造と幾何学構造を選択的に探査するための強力なツールです.
この発見により,FeMoco活性部位の電子特性についてより精密な理解が得られる.
HERFD XASとEXAFSは,基板相互作用による窒素酶内の動的変化を研究するための効果的な方法である.

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