Modelagem computacional aplicada ao estudo da cistina, selenocistina, teluriocistina, hidroxiureia e acido fólico

Abstract

Cystine is an amino acid which has in its structure two sulfur atoms which may be substituted by other elements such as selenium and tellurium. Experimental methods for the selenocistina and teluriocistina have been developed, though the role of these amino acids in the human metabolism are yet poorly understood. Amino acids such as cystine, selenocistina and teluriocistina have some geometric and electronic properties not determined, especially when it involves their conformations, minimum energy, distribution of atomic charges and the molecular volume. Other molecules such as hydroxyurea and folic acid, both used in the treatment of sickle cell anemia also have molecular and electronic properties that have not been fully explored. The aim of this study was to computational modeling of cystine, making substitutions in its structure, obtaining selenocistina, teluriocistina, and to study the geometric and electronic properties of hydroxyurea and folic acid, using Spartan'14 software that has ab initio methods Hartree-Fock (HF) and a set of basis functions STO-3G and 3-21G. Comparative structural modeling of conformers cystine and derivatives thereof, seleniocistina and teluriocistina, provided detailed information on the bond lengths, atomic charges and the relationship between the minimum energy and the molecular volume filling gaps in the structural characteristics of these amino acids . Research with the Hartree-Fock method and STO-3G base function, confirmed information on the X-ray refinement and atomic charges for related compounds. However, the geometry results obtained with the 3-21G basis function were not effective when compared to other results available in the literature. It was shown that C-Ch and Ch- Ch bond lengths increase with increasing ionic radius of the chalcogen. It has been shown that the Ch-Ch distances are independent of the substituents at most basic cystine compounds of chalcogen. It was purchased that the behavior of minimum energy presents a dependence on the molecular volume, as both depend on the variation of the dihedral angle C-Ch-Ch-C. Computer modeling as a tool for interpreting structure of hydroxyurea and folic acid by the semi-empirical method Hartree-Fock with the 6-31G basis function, provided the interpretation of the role of values of the atomic charges, geometrical parameters and interactions. The Spartan'14 using the Hartree- Fock method with the base function STO-3G to 3-21G chalcogenides and proved to be a suitable instrument for the structural prediction of bioactive molecules.