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Methods to Identify the NMR Resonances of the 13C-Dimethyl N-terminal Amine on Reductively Methylated Proteins
Published on: December 12, 2013
La captura de electrones resonantes por algunos ésteres de aminoácidos
Yury V Vasil'ev1, Benjamin J Figard, Douglas F Barofsky
1Department of Chemistry, Oregon State University, Corvallis, Oregon 97331.
Journal of the American Chemical Society
|October 20, 2009
Resumen
La captura de electrones resonantes revela nuevos mecanismos para la formación de iones negativos en los aminoácidos. Las preferencias conformamentales son clave para la fragmentación eficiente de los iones negativos progenitor en las reacciones de fase gaseosa.
Área de la Ciencia:
- Química Física es la química física.
- Física Química Física Química es la física de la química.
- La dinámica molecular es la dinámica molecular.
Sus antecedentes:
- La formación de iones negativos (NI) en los aminoácidos es crucial para comprender su comportamiento químico.
- Estudios anteriores vincularon las fragmentaciones eficientes de NI a los terminales C, pero los mecanismos de menor energía seguían siendo poco claros.
Objetivo del estudio:
- Aclarar nuevos mecanismos de formación de iones negativos en los aminoácidos y sus ésteres.
- Investigar el papel de las preferencias conformacionales en las vías de fragmentación de la fase gaseosa.
Principales métodos:
- Experimentos de captura de electrones resonantes a bajas y altas temperaturas.
- Análisis de las fragmentaciones de iones negativos (NI) en los ésteres de glicina, alanina y fenilalanina.
- Investigación teórica del acoplamiento entre los estados de iones dipolo-unidos y de valencia negativa.
Principales resultados:
- Se identificó un nuevo mecanismo que implica el acoplamiento entre los estados de iones dipolo-unidos y de valencia negativa para procesos de baja energía.
- Los aminoácidos no derivados se fragmentan a través de túneles de átomos de hidrógeno desde la superficie adiabática inferior, formando aniones carboxilatos.
- Los ésteres de aminoácidos se fragmentan a través del estado adiabático superior, formando análogos [M-X](-) NI sin penetración en la barrera.
Conclusiones:
- Las preferencias conformacionales influyen significativamente en la disociación de los iones negativos parentales.
- Los mecanismos identificados proporcionan una visión más profunda de los procesos fundamentales de captura de electrones y fragmentación en aminoácidos.
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