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El plegamiento inducido por el agua de 1,7-diamonioheptano

Maria Demireva¹, Jeremy T O'Brien, Evan R Williams

¹Department of Chemistry, University of California, Berkeley 94720-1460, USA.

Journal of the American Chemical Society

|June 20, 2012

Resumen

Los efectos de hidratación en el 1,7-diammoniumheptano muestran estructuras lineales con hasta 10 moléculas de agua. Los grupos más grandes (>12 moléculas de agua) adoptan conformaciones plegadas, lo que indica la solución de nanopartículas de agua de ambos grupos de aminas protonadas.

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:

Investigar el comportamiento estructural de las aminas protonadas en la fase gaseosa es crucial para comprender la dinámica de la solvación.
Las diaminas diprotonadas presentan desafíos únicos debido a sus múltiples sitios de carga.

Objetivo del estudio:

Para dilucidar las estructuras de hidratación de diprotonado 1,7-diaminoheptano y heptylamine protonado.
Para determinar cómo las moléculas de agua interactúan con grupos de aminas protonadas en grupos gaseosos.

Principales métodos:

Se empleó la espectroscopia de fotodisociación por infrarrojos (IRPD) para sondear los modos vibratorios.
La química computacional, incluidas las simulaciones de dinámica molecular, se utilizó para respaldar los hallazgos experimentales.

Principales resultados:

Pequeños grupos de 1,7-diamonioheptano-agua (hasta 10 moléculas de agua) exhiben estructuras lineales con solución alterna de grupos de aminas protonadas.
Los grupos más grandes (>12 moléculas de agua) muestran una transición a conformaciones plegadas, con ambas aminas protonadas solvadas por una sola nanogota de agua.
Las simulaciones de dinámica molecular confirman un aumento de la unión de hidrógeno en estructuras plegadas, compensando el aumento de la energía de Coulomb.

Conclusiones:

La hidratación conduce a cambios conformacionales en el 1,7-diaminoheptano diprotonado, favoreciendo estructuras plegadas con un mayor contenido de agua.
El equilibrio entre las interacciones coulombinas y el enlace de hidrógeno dicta la estructura de solvación preferida en estos grupos de aminas protonadas.

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