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La evidencia espectroscópica y teórica para la formación de anillos de oxazolona en la disociación inducida por
Nick C Polfer1, Jos Oomens, Sándor Suhai
1FOM Institute for Plasmaphysics Rijnhuizen, Edisonbaan 14, NL-3439 MN Nieuwegein, The Netherlands. polfer@rijnh.nl
Journal of the American Chemical Society
|December 8, 2005
Resumen
La disociación inducida por colisión de los péptidos protonados de leu-enkefalina forma anillos de oxazolona, no iones de acilio lineales. La espectroscopia infrarroja identificó tres estructuras distintas de oxazolona, lo que indica la transferencia de protones al extremo N.
Área de la Ciencia:
- Espectrometría de masas por espectrometría de masas.
- Física Química Física Química es el campo de la física química.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Los mecanismos de fragmentación de péptidos son cruciales para comprender la estructura y función de las proteínas.
- La disociación inducida por colisión (CID) es un método común para la fragmentación de péptidos en la espectrometría de masas.
- La formación de iones de fragmentos específicos proporciona información sobre las reorganizaciones de la columna vertebral de los péptidos.
Objetivo del estudio:
- Para investigar la estructura del fragmento b4+ de Leu-enkephalin generado por CID.
- Para determinar si la formación de anillos de oxazolona o las estructuras de acilo lineal prevalecen durante la CID.
- Para dilucidar la dinámica de transferencia de protones dentro del fragmento b4+.
Principales métodos:
- Se empleó espectroscopia infrarroja (IR) para analizar el fragmento b4+ de Leu-enkephalin.
- Se utilizó la disociación inducida por colisión (CID) para generar el fragmento b4+.
- El análisis del modo de estiramiento C = O en los espectros IR identificó estructuras distintas de oxazolona.
Principales resultados:
- CID de protonados Leu-enkephalin exclusivamente formado anillos de oxazolona, sin estructuras de acilio lineal observado.
- Se identificaron tres conformadores distintos de la oxazolona basados en las frecuencias de estiramiento características C=O.
- Los datos espectroscópicos indican la transferencia de protones desde el anillo de oxazolona hasta el péptido N-terminal.
Conclusiones:
- La formación de anillos de oxazolona es una vía dominante durante la EIC de la leu-enkefalina protonada.
- La transferencia de protones al extremo N acompaña a la formación de oxazolona.
- No se puede descartar la presencia de isómeros del péptido cíclico b4+ y justifica una mayor investigación.
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