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La transferencia de electrones versus la transferencia de protones en las reacciones de iones/iones en la fase
Harsha P Gunawardena1, Min He, Paul A Chrisman
1Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-2084, USA.
Journal of the American Chemical Society
|September 8, 2005
Resumen
La transferencia de electrones en las reacciones peptídico-iónico-iónico se favorece cinéticamente, pero se ve obstaculizada por las altas afinidades de electrones o los bajos factores de Franck-Condon. La transferencia de protones a menudo domina, con una barrera a la isomerización entre las vías de reacción.
Área de la Ciencia:
- Química Física es la química física.
- Física Química Física Química es la física de la química.
- Espectrometría de masas por espectrometría de masas.
Sus antecedentes:
- Las reacciones iónico-iónicas son cruciales para el análisis de péptidos, ya que implican vías competitivas de transferencia de protones y electrones.
- Comprender los mecanismos de transferencia de electrones es clave para interpretar los patrones de fragmentación en la espectrometría de masas.
- La teoría de Landau-Zener proporciona un marco para predecir las probabilidades de transferencia de electrones.
Objetivo del estudio:
- Evaluar las predicciones del modelo de Landau-Zener para la probabilidad de transferencia de electrones en las reacciones de iones péptidos/iones.
- Investigar la influencia de las propiedades de los aniones del reactivo en los resultados de la transferencia de electrones frente a la de protones.
- Explorar los factores que rigen la competencia entre la transferencia de electrones y la transferencia de protones.
Principales métodos:
- Reacciones de iones / iones realizadas utilizando un péptido modelo (KGAILKGAILR) y varios aniones de reactivo.
- Iones fragmentos analizados para identificar evidencia de transferencia de electrones o disociación de captura de electrones.
- Aplicó la teoría de Landau-Zener para modelar la energética y cinética de la transferencia de electrones.
Principales resultados:
- La transferencia de electrones fue evidenciada por iones fragmentos característicos, confirmando su ocurrencia.
- La transferencia de protones fue generalmente más exotérmica que la transferencia de electrones, favoreciéndola termodinámicamente.
- La probabilidad de transferencia de electrones se reduce por las altas afinidades de electrones (> 60-70 kcal / mol) y los bajos factores de Franck-Condon.
Conclusiones:
- El modelo de Landau-Zener, que incorpora criterios termodinámicos y geométricos, predice con precisión la viabilidad de la transferencia de electrones.
- Las afinidades específicas de los electrones y los factores de Franck-Condon son críticos para observar la transferencia de electrones.
- Existe una barrera de isomerización significativa entre los complejos que conducen a la transferencia de protones o electrones.
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