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La sorprendente rigidez de las moléculas de agua funcionalmente importantes enterradas en la región del grupo
Rongfu Zhang1,2, Timothy A Cross1,2, Xinhua Peng3
1National High Magnetic Field Laboratory, 1800 East Paul Dirac Drive, Tallahassee, Florida 32310, United States.
Journal of the American Chemical Society
|April 19, 2022
Resumen
Este estudio revela distintas especies acuáticas "confinadas" y "enlazadas" en las interfaces lipídicas utilizando la nueva RMN en estado sólido. Estos hallazgos desafían la visión del agua interfacial altamente móvil, mostrando poblaciones de agua estables en la escala de tiempo de milisegundos.
Área de la Ciencia:
- Biofísica y Química
- Biología estructural
- Dinámica del agua
Sus antecedentes:
- El agua interfacial en los sistemas biológicos es crucial para la función.
- Estudios anteriores sugieren un intercambio rápido (femtosegundos-nanosegundos) entre el agua interfacial y el agua a granel.
- Estudiar directamente el agua interfacial es un desafío debido a la dominación de la señal por el agua a granel.
Objetivo del estudio:
- Para sondear directamente el agua interfacial funcionalmente importante en los fosfolípidos hidratados.
- Caracterizar la dinámica y la estructura del agua en la interfaz lípido-agua.
- Desafiar la comprensión prevaleciente de la movilidad del agua interfacial.
Principales métodos:
- Desarrollo de una nueva técnica de resonancia magnética nuclear (RMN) en estado sólido.
- Se utilizó un imán de campo ultraalto (35,2 T) para una mayor sensibilidad.
- La supresión selectiva de la señal de agua a granel para aislar el agua interfacial.
Principales resultados:
- Se observaron dos especies de agua interfacial distintas: agua "confinada" y "confinada".
- El agua "confinada" mostró un cambio químico en el campo y tiempos de relajación alterados en comparación con el agua a granel.
- El agua "limitada" exhibió un movimiento severamente restringido y un distinto desplazamiento químico hacia arriba.
- Incluso el agua a granel exhibió una dinámica más lenta debido al intercambio con grupos lipídicos de interacción débil.
Conclusiones:
- Se ha demostrado la existencia de poblaciones de agua interfacial relativamente estables en la escala de tiempo de RMN (millisecondas).
- Proporciona una nueva oportunidad para estudiar la dinámica del agua en escalas de tiempo de milisegundos o más lentas en biomacromoléculas.
- Desafía la visión de larga data de que el agua interfacial es exclusivamente de intercambio rápido.
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