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Propiedades espectroscópicas de los radicales tirosilo en los dipeptidos
Idelisa Ayala1, Kevin Range, Darrin York
1Department of Biochemistry, University of Minnesota, 1479 Gortner Avenue, St. Paul, Minnesota 55108-1022, USA.
Journal of the American Chemical Society
|May 9, 2002
Resumen
Se generaron radicales de tirosina redox-activos mediante fotólisis UV. Se observaron interacciones inesperadas entre el sistema pi del radical tirosilo y los grupos amino/amida a través de la espectroscopia EPR y FT-IR.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- La espectroscopia es una técnica de espectroscopia.
- Química de los radicales de proteínas Química de los radicales de proteínas
Sus antecedentes:
- Los residuos de tirosina redox-activa son cruciales para la transferencia de electrones en enzimas como el fotosistema II.
- El estudio de la estructura de los aminoácidos redox-activos en las proteínas es esencial para comprender los mecanismos de las enzimas.
- La resonancia magnética y la espectroscopia vibratoria son técnicas clave para esta investigación.
Objetivo del estudio:
- Para investigar la estructura de los radicales tirosilo generados por la fotólisis ultravioleta.
- Para explorar las interacciones entre el radical tirosilo y los grupos amino o amida adyacentes en péptidos.
- Proporcionar una base espectral para la interpretación de los radicales tirosílicos basados en proteínas.
Principales métodos:
- Fotólisis ultravioleta a 77 K para generar radicales tirosilo a partir de tirosinato policristalino o dipeptidos.
- Espectroscopia de Resonancia Paramagnética Electrónica (EPR) para el estudio de las estructuras radicales.
- Espectroscopia infrarroja inducida por reacción de la Transformación de Fourier (FT-IR) con etiquetado isotópico ((13) C, (15) N) para sondear cambios estructurales.
Principales resultados:
- Los resultados EPR y FT-IR de la tirosina marcada con (13) C confirmaron la generación de un radical tirosílico neutro.
- Los cambios inesperados de isótopos en las muestras etiquetadas con (15) N indicaron una interacción entre el sistema pi del radical tirosílico y el grupo amino.
- Los espectros de los dipeptidos mostraron interacciones dependientes de la secuencia entre el radical tirosílico y el enlace amídico.
Conclusiones:
- Un mecanismo de polarización de espín probablemente media la interacción entre el radical tirosílico y los grupos amino/amida, detectado a través de cambios en las constantes de fuerza NH.
- Los cálculos funcionales de densidad apoyan la deslocalización de la densidad de espín a los grupos amino y carboxilato, influenciados por la conformación.
- Estos hallazgos avanzan en la interpretación espectral de los radicales tirosilo redox-activos en los sistemas biológicos.
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