リバーシブル・プロトナート・レスト・ステート・オブ・ナイトロゲネーゼ・アクティブ・サイト
Christine N Morrison1, Thomas Spatzal1, Douglas C Rees1
1Division of Chemistry and Chemical Engineering and ‡Howard Hughes Medical Institute, California Institute of Technology , Pasadena, California 91125, United States.
Journal of the American Chemical Society
|July 11, 2017
まとめ
窒素酸モリブデン鉄 (MoFe) タンパク質は,低pHで逆転可能な構造および電子変化を経験し,活性部位のプロトン化を示唆する. これらの発見は,窒素の固定メカニズムに光を当てます.
科学分野:
- 生物化学
- 構造生物学
- バイオ有機化学
背景:
- 窒素酵素活性部位のプロトネーションは,基板の還元に不可欠である.
- これらの陽子状態を理解することは,窒素固定機構の解明の鍵です.
研究 の 目的:
- 窒素酸モリブデン鉄 (MoFe) タンパク質の低pHの振る舞いを特徴づけるために.
- プロトネーションに関連した構造的および電子的変化を調査する.
主な方法:
- X線結晶学と電子パラマグネティック共振 (EPR) スペクトロスコーピーを用いた.
- Azotobacter vinelandii (Av) とClostridium pasteurianum (Cp) のMoFeタンパク質をpH4. 5~8で研究した.
主要な成果:
- 低pH (4.5-6) で,FeMoコファクターの周りのサイドチェーンの再配置が誘発される.
- EPRのスペクトロスコピーは,触媒の周回状態に似た新しいS = 3/2スピンシステムを明らかにした.
- FeMo-コファクターベルト硫黄 (S3AまたはS5A) の潜在的なプロトネーションサイトが特定されました.
- 観察された構造的および電子的変化は相関し,可逆的であった.
- AvとCp MoFeのタンパク質の構造的な再編成の違いが認められた.
結論:
- 静止中の窒素酶の状態 (E0H+と呼ばれる) の逆転性プロトネーションが起こる可能性が高い.
- 構造的および電子的な変化は,窒素固定に関する機械的洞察を提供します.
- 複数の窒素酵素種を調査することで,活性部位のプロトネーションメカニズムの変化が浮き彫りにされる.
さらに関連する動画
関連する概念動画
Nitriles to Carboxylic Acids: Hydrolysis
5.1K
Nitriles undergo acid-catalyzed hydrolysis or base-catalyzed hydrolysis to form a carboxylic acid. These reactions proceed via an amide intermediate.
5.1K
Structure of Amines
3.4K
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are...
3.4K
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism
5.0K
Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.
5.0K
Aldehydes and Ketones with Amines: Imine Formation Mechanism
8.7K
Imine formation involves the addition of carbonyl compounds to a primary amine. It begins with the generation of carbinolamine through a series of steps involving an initial nucleophilic attack and then several proton transfer reactions. The second part includes the elimination of water, as a leaving group, to give the imine.
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
Imines are formed under mildly acidic conditions. A pH of 4.5 is ideal for the reaction.
If the pH is low or the solution is too acidic, the reaction slows down in the...
8.7K
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview
4.0K
Nitrous acid and nitric acids are two types of acids containing nitrogen, among which nitrous acid is weaker than nitric acid. Nitrous acid with a pKa value of 3.37 ionizes in water to give a nitrite ion and the hydronium ion.
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by...
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by...
4.0K
Proton (¹H) NMR: Chemical Shift
3.7K
Organic molecules primarily contain carbon and hydrogen atoms. While all the hydrogen isotopes are NMR-active, protium or hydrogen-1 is the most abundant. It has a significant energy separation between its nuclear spin states due to its large gyromagnetic ratio. As per Boltzmann's distribution, an increase in the energy separation implies a greater excess population of nuclei available for excitation, resulting in a strong NMR absorption signal.
Absorption signals of all the protium nuclei...
Absorption signals of all the protium nuclei...
3.7K
![Protein Film Infrared Electrochemistry Demonstrated for Study of H2 Oxidation by a [NiFe] Hydrogenase](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F55858.jpg&w=3840&q=50)

