Estudo ab-initio da a-alanina em meio aquoso

• Autor(a) principal: Sambrano, Julio Ricardo [UNESP]
• Data de Publicação: 1999
• Outros Autores: Souza, Aguinaldo Robinson de [UNESP], Queralt, Joaquim Josep, Andrés, Juan, Longo, Elson [UNESP]
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Repositório Institucional da UNESP
• Texto Completo: http://dx.doi.org/10.1590/S0100-40421999000400006; http://hdl.handle.net/11449/27562
• topic: ab initio; a-alanine; solvent

Ab initio Hartree-Fock (HF), Density Functional (B3LYP) and electron correlation (MP2) methods have been used to caracterize the aqueous medium intramolecular hydrogen bond in a-alanine. The 6-31G* and 6-31++G** were taken from Gaussian94 library. We were concerned on the structure of three conformers of a-alanine, in their neutral form plus on the structure of the zwitterionic form (Z). The Z structure is a stationary point at the HF/6-31G* level but it is not when diffuse functions and electron correlation are included. This results shows that the Z form does not exist in the gas phase. The inclusion of solvent effects changed significantly the results obtained in gas phase, therefore this inclusion make the Z form a stationary point within all level of theory, and the relative energy depends dramatically on the level of calculation.