ONIOM ((DFT:MM) の2ヒドロキシエチルフォスフォン酸二酸化酵素の研究:何が異なる基質の運命を決定するのか?
1Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore. hirao@ntu.edu.sg
Journal of the American Chemical Society
|August 31, 2011
まとめ
酵素は,異なる反応経路により,類似した基板から異なる製品を産出します. 陽子結合電子移転 (PCET) は,これらの酵素反応において,共通根幹の中間物質が形成された後の結果を決定する.
科学分野:
- バイオケミストリー バイオケミストリー
- 酵素学 酵素学とは
- コンピューティング・ケミストリー
背景:
- 酵素は様々な反応を触媒にしますが,微妙な基板の違いが多種多様な製品にどのようにつながるのかを理解することは極めて重要です.
- 2-ヒドロキシエチルホスフォン酸二酸化酵素 (HEPD) は,2-ヒドロキシエチルホスフォン酸 (2-HEP) と1-HEPとの異なる反応を触媒化し,異なる製品を生成します.
研究 の 目的:
- HEPDと2-HEPおよび1-HEPの異なる反応メカニズムを解明する.
- 酵素経路と製品形成を区別する重要な要因を特定する.
主な方法:
- 酵素反応をモデル化し分析するために,ONIOM (((DFT:MM)) の計算方法を使用しました.
- 分子レベルでの反応機構を調査し,中間生成と電子移転プロセスに焦点を当てました.
主要な成果:
- 両方の基質の同じ初期処理で生成された類似の基質中間物質を特定した.
- 陽子結合電子移転 (PCET) が1HEP反応では活性化しているが,2HEP反応では活性化していないことが明らかになった.
- ラジカル中間物質の形成後の2-HEP反応において,代替経路が採用されていることが示された.
結論:
- HEPDの反応経路と産物特異性を決定する際に,陽子結合電子伝送 (PCET) の重要な役割.
- サブストラット相互作用の微妙な差異は,共通のラジカル中間生成の後,明確な機械的運命を導きます.
さらに関連する動画
関連する概念動画
03:08Hydroboration-Oxidation of Alkenes
In addition to the oxymercuration–demercuration method, which converts the alkenes to alcohols with Markovnikov orientation, a complementary hydroboration-oxidation method yields the anti-Markovnikov product. The hydroboration reaction, discovered in 1959 by H.C. Brown, involves the addition of a B–H bond of borane to an alkene giving an organoborane intermediate. The oxidation of this intermediate with basic hydrogen peroxide forms an alcohol.
02:36Regioselectivity and Stereochemistry of Hydroboration
A significant aspect of hydroboration–oxidation is the regio- and stereochemical outcome of the reaction.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
01:33Regioselective Formation of Enolates
As depicted in the figure below, the unsymmetrical ketones can form two possible enolates: less substituted or more substituted enolates. Usually, the thermodynamic enolates are formed from the more substituted α-carbon atom, while the kinetic enolates are formed faster by deprotonation from the less substituted position. The thermodynamic enolates have lower energy, so they are more stable. But the energy required to form kinetic enolates is less.
02:44Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide
Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
02:34Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration
The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
02:04Oxidation of Alkenes: Anti Dihydroxylation with Peroxy Acids
Diols are compounds with two hydroxyl groups. In addition to syn dihydroxylation, diols can also be synthesized through the process of anti dihydroxylation. The process involves treating an alkene with a peroxycarboxylic acid to form an epoxide. Epoxides are highly strained three-membered rings with oxygen and two carbons occupying the corners of an equilateral triangle. This step is followed by ring-opening of the epoxide in the presence of an aqueous acid to give a trans diol.