Fulco, Umberto LainoMedeiros, Mabelle de Araújo2023-01-112023-01-112022-12-13MEDEIROS, Mabelle de Araújo. Análise estrutural e eletrônica de pequenos peptídeos de Alanina: um estudo de métodos in silico. 2022. 62 f. Trabalho de Conclusão de Curso (Graduação em Biomedicina) - Centro de Biociências, Universidade Federal do Rio Grande do Norte, Natal, 2022.https://repositorio.ufrn.br/handle/123456789/50915Amino acids are the monomers of proteins and, for this reason, their geometry can influence the protein structure and therefore its function. Alanine is one of the most important amino acids, present in great quantities in proteins and being widely used in computational studies due to its characteristics, that include being the smallest chiral amino acid. For these reasons, we analyzed four structures formed exclusively by alanine, being composed of one, two, three and four residues (ALA1, ALA2, ALA3 and ALA4, respectively). These structures were subjected to DFT calculations using the M062X, B3LYP, B97D, WB97XD, BHandHLYP a PBE functionals, ab initio calculations using the hartree-fock (HF) and MP2 methods, with the 6-31+g(d) basis set for both DFT and ab initio calculations, and semi-empirical calculations, namely AM1 and PM3. Optimization of their geometry was performed in order to compare how increasing the chain influenced the structure of the alanine residues and what was the effect of each method on the parameters studied. We observed that internal geometry (bond length and angles) was almost not affected by the calculation method applied, whereas the number of the residues in the peptide chain can slightly change the description of the angles, with AM1 and MP2 showing the lowest bond angle deviations. The Mülliken charges were quite similar when comparing the computation methods and the four groups of peptide chain, albeit semiempirical outcomes provided slightly different atomic charges when compared to DFT, HF and MP2 ones. In the total energy, we observed that AM1, PM3 and HF calculations presenting the highest total energies, whereas B3LYP and WB97XD showed the lowest. Finally, the frontier molecular orbitals were the feature most affected by the choice of the computation method.Attribution-NonCommercial-NoDerivs 3.0 Brazilhttp://creativecommons.org/licenses/by-nc-nd/3.0/br/AlaninaAlanineMecânica QuânticaQuantum MechanicsGeometria de aminoácidosAmino acid geometrySimulação computacionalComputational simulationDFTAb initioSemi-empíricoSemi-empiricalbachelorThesisCNPQ::CIENCIAS BIOLOGICAS::BIOFISICA