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Estructuras y entalpías de hidratación de la glutamina cationizada y sus análogos estructurales en la fase gaseosa
Andrew S Lemoff1, Matthew F Bush, Chih-Che Wu
1Department of Chemistry, University of California, Berkeley, California 94720-1460, USA.
Journal of the American Chemical Society
|July 21, 2005
Resumen
Los iones de litio y sodio se unen a la glutamina en una forma no zwitteriónica, con moléculas de agua débilmente asociadas. Esta estructura de unión es confirmada por experimentos de disociación infrarroja y cálculos teóricos.
Área de la Ciencia:
- Química Física es la química física.
- Química biofísica y bioquímica.
- Química computacional es la química computacional.
Sus antecedentes:
- Los aminoácidos como la glutamina juegan un papel crucial en los sistemas biológicos.
- Comprender la solvación y las interacciones de los iones metálicos con los aminoácidos es vital para la bioquímica.
- Estudios anteriores han explorado las interacciones de iones metálicos con derivados de aminoácidos.
Objetivo del estudio:
- Para investigar las estructuras de los complejos de glutamina con litio y sodio, con y sin agua.
- Para determinar la energía de unión de las moléculas de agua a estos complejos.
- Aclarar el papel de las formas zwitteriónicas frente a las no zwitteriónicas en la complejación de iones metálicos.
Principales métodos:
- Se utilizaron experimentos de disociación radiativa infrarroja de cuerpo negro (BIRD) para sondear la pérdida de agua.
- Se aplicó el modelado de ecuaciones maestras para determinar las energías de disociación umbral (E(o)).
- Los cálculos de la teoría funcional de la densidad (DFT) se emplearon para modelar estructuras complejas y energéticas.
Principales resultados:
- Las energías de disociación umbral para la pérdida de agua de la glutamina litiada y sodiada se determinaron como 63 ± 1 y 53 ± 1 kJ / mol, respectivamente.
- Estos valores indican una estructura no zwitteriónica para la glutamina en estos complejos metálicos.
- Se encontró que las energías de unión del agua eran más bajas que las de las formas zwitteriónicas, lo que sugiere una complicación no zwitteriónica.
Conclusiones:
- La glutamina litiada y sodiada adopta predominantemente estructuras no zwitteriónicas.
- El ion metálico se coordina con la columna vertebral del aminoácido y la cadena lateral de la amida oxígeno.
- Las moléculas de agua se unen menos fuertemente a estos complejos no zwitteriónicos en comparación con las formas zwitteriónicas.
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