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Coordinación axial del disolvente en "base-fff" cob(II) alamina y co(II) corrinados relacionados revelados por 2D-EPR
Sabine Van Doorslaer1, Gunnar Jeschke, Boris Epel
1Laboratory of Physical Chemistry, ETH Hönggerberg, CH-8093 Zurich, Switzerland.
Journal of the American Chemical Society
|May 8, 2003
Resumen
Los corrinatos de cobalto, como los intermediarios de cobalto en las reacciones de la coenzima B12, muestran estructuras dependientes del disolvente. Las técnicas avanzadas de EPR y ENDOR revelan cambios en la ligadura axial y la coordinación influenciados por las propiedades del disolvente.
Área de la Ciencia:
- Coordinación Química de la Coordinación
- Química bioorgánica Química bioorgánica.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los corrinatos de cobalto (II) son intermediarios cruciales en las reacciones catalizadas por la coenzima B12.
- Comprender su estructura en solución es clave para dilucidar los mecanismos enzimáticos.
- La solubilidad del éster de cobalto permite estudios controlados de los efectos del disolvente en los corrinados de cobalto.
Objetivo del estudio:
- Para investigar la estructura de la solución de los corrinados de cobalto, específicamente el éster de cobalto y la alumina de cobalto (B12r).
- Para determinar el estado de coordinación (ligación axial) del cobalto (II) corrinatos en varios disolventes.
- Explorar la influencia de las propiedades del disolvente y las transiciones de fase en la estructura del cobalto (II) corrinato.
Principales métodos:
- Utilizó una combinación de espectroscopia de onda continua (CW) y resonancia paramagnética de electrones de pulso (EPR).
- Empleado pulso ENDOR (doble resonancia nuclear de electrones) en varias frecuencias de microondas.
- Interpretación de datos con soporte con cálculos de la Teoría Funcional de Densidad (DFT).
Principales resultados:
- Proporcionó pruebas claras de la ligadura axial en el éster de Cob{II} y la cob{II}alamina (B12r) sin base a través de diferentes solventes.
- Se ha demostrado que los parámetros EPR (valores de g, acoplamientos hiperfinos) son indicadores sensibles de la ligadura con solventes.
- Se observó un cambio estructural dependiente de la temperatura en el éster de cobalto en el metanol, pasando de la coordinación cinco a seis por debajo de 100 K debido a la transición de fase del metanol.
Conclusiones:
- Las características del disolvente impactan significativamente en la estructura de coordinación de los corrinados de cobalto.
- El comportamiento de coordinación del éster de cobalto (II) y el B12r de base en solución refleja sus estructuras electrónicas.
- Las comparaciones entre los estudios de soluciones y los cofactores incrustados en proteínas requieren una cuidadosa consideración de los efectos del disolvente.
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