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¿Tiene el par de bases A.T. o G.C mayor estabilidad? Cuantificación de los efectos de las interacciones CH...O e
Jordan R Quinn1, Steven C Zimmerman, Janet E Del Bene
1Department of Chemistry, Roger Adams Laboratory, University of Illinois, 600 South Mathews Avenue, Urbana, Illinois 61801, USA.
Journal of the American Chemical Society
|January 25, 2007
Resumen
Los pares de bases adenina-timina (AT) han mejorado la estabilidad debido a una interacción CH ... O, contribuyendo aproximadamente 2-2.5 kcal mol-1. Esta interacción también favorece a Hoogsteen sobre la geometría de Watson-Crick en pares de bases AT.
Área de la Ciencia:
- La bioquímica es la bioquímica.
- Química computacional es la química computacional.
- Biología Molecular Biología Molecular
Sus antecedentes:
- Las parejas de bases de ADN y ARN son fundamentales para el almacenamiento y la transferencia de información genética.
- La estabilidad relativa de los pares de bases A.T y G.C es crucial para comprender la estructura y función de los ácidos nucleicos.
- Estudios anteriores se han centrado principalmente en las interacciones de enlace de hidrógeno en pares de bases.
Objetivo del estudio:
- Investigar si los pares de bases A.T/U y G.C exhiben una estabilidad mejorada en comparación con complejos similares enlazados con hidrógeno.
- Para cuantificar la contribución de interacciones específicas, como los contactos CH...O, a la estabilidad del par base.
- Explorar las preferencias geométricas del emparejamiento de bases AT y el papel de las interacciones no canónicas.
Principales métodos:
- Desarrolló una relación empíricamente basada que correlaciona la estabilidad global compleja (-grados DeltaG) con las interacciones de los componentes.
- Empleados cálculos ab initio en el nivel MP2/6-31+G.
- Utilizó un enfoque de ciclo de doble mutante.
- Investigó modelos complejos de adenina con ceteno y ácido isocánico.
Principales resultados:
- El enfoque fenomenológico sugirió una estabilidad adicional de ca. 2-2.5 kcal mol-1 para pares de bases A.T debido a una interacción del grupo CH...O.
- Los estudios ab initio indicaron una preferencia por la geometría de Hoogsteen sobre la geometría de Watson-Crick en el AT por ca. 1 kcal mol-1.1, es decir, 1 kcal por mol-1.
- Los factores que contribuyen a la preferencia de Hoogsteen incluyen un contacto CH...O más corto, una alineación dipolar favorable y una repulsión reducida.
Conclusiones:
- Los pares de bases A.T poseen una estabilidad mejorada más allá de los enlaces de hidrógeno tradicionales, atribuida a una interacción CH...O.
- La interacción CH...O juega un papel importante en la preferencia geométrica del emparejamiento de bases AT.
- Los hallazgos computacionales y empíricos apoyan la estabilidad mejorada de los pares de bases AT debido a las interacciones no canónicas.
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