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Dinámica de isomerización hacia adelante de segunda oportunidad del cianobacteriocromo rojo/verde NpR6012g4 de Nostoc
Peter W Kim1, Lucy H Freer, Nathan C Rockwell
1Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, USA.
Journal of the American Chemical Society
|November 24, 2011
Resumen
El cianobacteriocromo NpR6012g4 exhibe una isomerización ultrarrápida de Z a E. Un mecanismo de estado fundamental de "segunda oportunidad" explica su alto rendimiento cuántico, que implica un intermediario metastable que completa la isomerización.
Área de la Ciencia:
- La fotoquímica es la fotoquímica.
- La biofísica es la biofísica.
- La espectroscopia es una técnica de espectroscopia.
Sus antecedentes:
- Las cianobacteriocromas son fotorreceptores involucrados en la detección de la luz.
- Comprender su fotodinámica es crucial para descifrar las respuestas biológicas a la luz.
- NpR6012g4 de Nostoc punctiforme es un sistema modelo para el estudio de estos procesos.
Objetivo del estudio:
- Para investigar la fotodinámica de la isomerización ultra rápida de Z a E de NpR6012g4.4.
- Para dilucidar el mecanismo detrás del alto rendimiento cuántico del paso de isomerización primaria.
Principales métodos:
- Se empleó la espectroscopia de absorción transitorio bomba-dump-sonda.
- Se utilizó un pulso de descarga de 2 ps para sondear las poblaciones de estado excitado y fotoproducto.
- Se aplicó un análisis global multicomponente a los datos espectroscópicos.
Principales resultados:
- Un pulso de descarga de 2 ps agotó el 21% de la población en estado excitado y el 11% del fotoproducto Lumi-R.
- Se observó un intermedio del estado fundamental desplazado al rojo (GSI), asignado a un estado metastable.
- Se generó Lumi-R adicional a partir del GSI a través del cruce de la barrera térmica.
Conclusiones:
- La discrepancia observada en el agotamiento sugiere un mecanismo de isomerización de "segunda oportunidad".
- Esta dinámica de estado fundamental explica el alto rendimiento cuántico (40%) para la isomerización primaria de Z a E.
- Los hallazgos proporcionan información sobre la señalización eficiente impulsada por la luz de las cianobacteriocromas.
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