Video Experimental Relacionado
Updated: May 31, 2026
08:23
Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds
Published on: February 16, 2022
Un nuevo intermedio paramagnético formado durante la reacción del nitrito con la desoxihemoglobina
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
Resumen
Los investigadores identificaron una nueva especie de hemoglobina paramagnética, ·SHb(II) NO, formada durante la reducción de nitrito. Este intermediario explica las interacciones estables nitrito-hemoglobina y contribuye a la liberación de óxido nítrico (NO) para la vasodilatación.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Fisiología Fisiología Fisiología.
- Biología Química Biología química.
Sus antecedentes:
- La reducción de nitrito por la hemoglobina desoxigenada está relacionada con la vasodilatación inducida por los glóbulos rojos.
- El mecanismo preciso de este proceso y la estabilidad de los intermedios de reacción siguen sin estar claros.
Objetivo del estudio:
- Para investigar la formación y las propiedades de un intermediario de transferencia de electrones propuesto, ·SHb(II) NO, durante la reducción de nitrito por hemoglobina desoxigenada.
- Aclarar el mecanismo detrás de la estabilidad de los intermediarios de reacción nitrito-hemoglobina y su papel en la bioactividad del óxido nítrico (NO).
Principales métodos:
- Se empleó la espectroscopia de resonancia paramagnética de electrones (EPR) para detectar especies paramagnéticas.
- Los experimentos involucraron el bloqueo del grupo tiol β-93 con N-etil-maleimida y el uso de carboxipeptidasa-A para estabilizar la conformación R-cuaternaria.
Principales resultados:
- El análisis EPR confirmó la formación de ·SHb(II) NO, caracterizada por señales tanto del NO unido al hemo como de un radical tilio.
- Esta especie existe en equilibrio con un intermediario híbrido (Hb(II) NO(+) Hb(III) NO), estabilizando aún más la unión al NO.
- La incubación a baja temperatura (-20 °C) cambió el equilibrio, apoyando el mecanismo propuesto.
Conclusiones:
- Se ha identificado una nueva especie paramagnética de NO-hemoglobina, ·SHb(II) NO.
- Este intermedio explica la estabilidad de los productos de reacción y la acumulación de NO bioactivo durante la reducción de nitrito.
- Los hallazgos proporcionan una vía para la formación de hemoglobina S-nitrolizada (SNOHb), un conocido vasodilatador.
Más Videos Relacionados
Videos de Conceptos Relacionados
01:202° 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.
01:24Hemoglobin
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...
01:261° 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...
01:371° 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.
01:19Nitrosation 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.
01:13meta-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...