在酸盐与脱氧血球蛋白反应过程中形成的新型磁性中间体
Maria T Salgado1, Somasundaram Ramasamy, Antonio Tsuneshige
1Molecular Dynamics Section, National Institute on Aging, NIH, Baltimore, Maryland 21224, USA.
Journal of the American Chemical Society
|July 16, 2011
概括
研究人员确定了一种新的偏磁性血红蛋白物种,SHb (II) NO,在化物还原过程中形成. 这种中间体解释了稳定的亚酸盐-血红蛋白相互作用,并有助于释放氧化 (NO) 进行血管扩张.
科学领域:
- 生物化学 生物化学
- 生理学 生理学 生理学
- 化学生物学 化学生物学
背景情况:
- 通过脱氧化血红蛋白减少酸盐与红细胞诱导的血管扩张有关.
- 这个过程的确切机制和反应中间体的稳定性仍然不清楚.
研究的目的:
- 通过去氧化血红蛋白减少酸盐的过程中,研究一种拟议的电子转移中间体,SHb (II) NO的形成和特性.
- 阐明酸盐-血红蛋白反应中间体稳定性背后的机制及其在氧化 (NO) 生物活性中的作用.
主要方法:
- 电子偏磁共振 (EPR) 光谱法用于检测偏磁物种.
- 实验包括用N-乙基-马利胺胺阻断β-93醇组,并使用碳氧酶-A来稳定R-四分体构造.
主要成果:
- 经过EPR分析,证实了 ·SHb(II) NO 的形成,其特征是来自血结合的NO和一个基的信号.
- 这种物种与混合中间体 (Hb(II) NO(+) Hb(III) NO) 处于平衡状态,进一步稳定了NO结合.
- 低温化 (-20°C) 改变了平衡,支持了拟议的机制.
结论:
- 已经确定了一种新的NO-血红蛋白性磁性物种,SHb (II) NO.
- 这种中间体解释了反应产品的稳定性和在化物还原过程中生物活性NO的积累.
- 这些发现为S-化血红蛋白 (SNOHb) 的形成提供了一条途径,这是一个已知的血管扩张剂.
相关概念视频
2° Amines to N-Nitrosamines: Reaction with NaNO2
Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.
Hemoglobin
Hemoglobin is a globular protein made up of four subunits. Two of these subunits are alpha chains, and the other two are beta chains. Each subunit contains a molecule of heme, which has an iron atom and can bind to oxygen. When an oxygen molecule binds to one heme group, it changes the shape of hemoglobin, making it easier for the other heme groups to bind oxygen as well.
When all four heme groups are bound to oxygen, the resulting molecule is called oxyhemoglobin. As a result, arterial blood...
When all four heme groups are bound to oxygen, the resulting molecule is called oxyhemoglobin. As a result, arterial blood...
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview
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 water loss...
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 water loss...
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism
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.
Nitrosation of Enols
The nitrosation reaction is one of the methods of preparing 1,2-diketones. The enol tautomer of the starting ketone reacts with sodium nitrite in hydrochloric acid, generating the 1,2-diketone after hydrolysis.
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H
All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...


