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Cambios conformacionales inducidos por la transferencia de protones y fusión en péptidos diseñados en la fase gaseosa
Motoya Kohtani1, Thaddeus C Jones, Rajagopalan Sudha
1Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, USA.
Journal of the American Chemical Society
|June 1, 2006
Resumen
Las conformaciones del péptido cambian con la temperatura debido a la transferencia de protones. Los péptidos arginina-alanina-lisina (RAK) y arginina-alanina-histidina (RAH) muestran transiciones hélice-glóbulo dependientes de la temperatura y fusión de hélice.
Área de la Ciencia:
- La biofísica es la biofísica.
- Química computacional es la química computacional.
- Ciencia de las proteínas Ciencia de las proteínas.
Sus antecedentes:
- Los péptidos son cadenas cortas de aminoácidos.
- La transferencia de protones puede influir en la estructura del péptido.
- Comprender las conformaciones de los péptidos es clave para el plegamiento de las proteínas.
Objetivo del estudio:
- Para investigar las conformaciones dependientes de la temperatura de los péptidos protonados arginina-alanina-lisina (RAK) y arginina-alanina-histidina (RAH).
- Explorar el papel de la transferencia intramolecular de protones en la conducción de cambios conformacionales.
- Para caracterizar las transiciones hélice-glóbulo y los fenómenos de fusión de hélice.
Principales métodos:
- Análisis de la conformación de la fase gaseosa de péptidos protonados (RA15K, RA20K, RA15H) utilizando variación de la temperatura.
- Observación de transiciones estructurales controladas cinéticamente por debajo de 400 K.
- Análisis de las transiciones hélice-glóbulo y de la fusión de la hélice alrededor de 500 K.
Principales resultados:
- Se observaron transiciones controladas cinéticamente: hélice a glóbulo para RA15H, glóbulo a hélice para RA15K y RA20K por debajo de 400 K.
- La conformación globular se expande y se vuelve entropicamente favorecida a temperaturas más altas.
- Las hélices RA15K y RA20K experimentan amplias transiciones de fusión alrededor de 500 K, que se estrechan con el aumento del tamaño del péptido.
- RA15K doblemente protonado muestra una conformación parecida a una mancuerna a altas temperaturas debido a la repulsión de residuos.
Conclusiones:
- La transferencia intramolecular de protones es un factor clave de los cambios conformacionales en estos péptidos.
- La temperatura influye significativamente en la estructura del péptido, favoreciendo los estados globulares expandidos y impulsados entrópicamente.
- El tamaño del péptido afecta a la cooperatividad de la fusión de la hélice, con péptidos más grandes que muestran transiciones más estrechas.
- La movilidad de los protones está probablemente involucrada en la transición de fusión de las conformaciones helicoidales.
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