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Resonancia paramagnética de electrones y espectroscopia de Mössbauer y análisis de la teoría funcional de la densidad
Rupal Gupta1, David C Lacy, Emile L Bominaar
1Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
Journal of the American Chemical Society
|May 12, 2012
Resumen
Este estudio demuestra la primera detección y cuantificación de especies de hierro de alto espín (IV) -oxo en complejos no hemo utilizando espectroscopia de resonancia paramagnética de electrones (EPR). Estos hallazgos avanzan en nuestra comprensión de la covalencia de enlaces de hierro-oxo y los sitios activos de la enzima.
Área de la Ciencia:
- Química bioorgánica Química bioorgánica.
- La espectroscopia es una técnica de espectroscopia.
- Química computacional es la química computacional.
Sus antecedentes:
- Las especies de hierro de alto espín ((IV) -oxo son oxidantes cruciales en las enzimas de hierro no hemo, pero se comprenden menos que las contrapartes de hemo.
- La caracterización de estos intermediarios reactivos es esencial para la comprensión de los mecanismos enzimáticos.
Objetivo del estudio:
- Caracterizar los complejos de hierro (IV) -oxo de alto espín utilizando técnicas espectroscópicas avanzadas.
- Establecer la espectroscopia de resonancia paramagnética de electrones (EPR) como un método viable para detectar y cuantificar estas especies.
- Para investigar la estructura electrónica y la unión en el enlace hierro-oxó.
Principales métodos:
- Caracterización detallada utilizando espectroscopia de Mössbauer y resonancia paramagnética de electrones de doble frecuencia / doble modo (EPR).
- Simulaciones espectrales EPR cuantitativas para determinar la división de campo cero (D) y la concentración de especies.
- (17) Experimentos de enriquecimiento de isótopos de O para investigar las interacciones hiperfinas.
- Cálculos de la teoría funcional de la densidad (DFT) para la comparación con datos experimentales.
Principales resultados:
- Se detectaron y cuantificaron con éxito las primeras señales EPR de un complejo de hierro ((IV) -oxo de alto espín ([Fe ((IV) H ((3) buea ((O))))).
- El parámetro de campo cero D se determinó como +4.7 cm(-1), con cálculos de DFT que apoyan el valor experimental.
- Los experimentos de enriquecimiento de isótopos proporcionaron constantes hiperfinas, lo que permitió la primera determinación experimental de la polarización de espín en el enlace Fe-oxo de complejos no hemo, lo que indica una covalencia significativa.
- La espectroscopia de Mössbauer proporcionó parámetros nucleares detallados para el complejo hierro-oxógeno, consistentes con los cálculos de DFT.
Conclusiones:
- La espectroscopia de resonancia paramagnética de electrones (EPR, por sus siglas en inglés) es una poderosa herramienta para detectar y cuantificar las especies de hierro de alto espín (IV) -oxo en complejos no heme.
- El enlace Fe-oxo en estos complejos exhibe una covalencia significativa, como lo demuestra la polarización de espín determinada.
- Este trabajo proporciona información fundamental sobre la estructura y la reactividad de los intermediarios clave en las enzimas de hierro no hemo.
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