Navegando por Autor "Caetano, E. W. S."
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Artigo Electronic specific heat of an a3-helical polypeptide and its biochemical variants(Elsevier, 2012-07-23) Bezerril, Leonardo Mafra; Mendes, G. A.; Albuquerque, Eudenilson Lins de; Fulco, Umberto Laico; Caetano, E. W. S.; Freire, V. N.We perform a theoretical study of the temperature dependent electronic specific heat at constant volume CV ðTÞ for a fibrous a3-helical polypeptide, which has the amino acid sequence (Leu-Glu-Thr-Leu-Ala-Lys- Ala)3, considering only its primary structure. We focus also on two different variants of the a3-helical polypeptide, namely those with (5Qa3 variant, mutation Ala5Gln) and without (7Qa3 variant, mutation Ala7Gln) fibrous assemblies. The energy spectra are calculated using a two-dimensional Schrödinger equation within a tight-binding approximation in which the isolated amino acid vertical ionization energy and the hopping terms are found using density functional theory computationsArtigo A quantum chemistry investigation of a potential inhibitory drug against the dengue virus(Royal Society of Chemistry, 2016) Ourique, G. S.; Vianna, Jéssica de Fátima; Lima Neto, José Xavier de; Oliveira, J. I. N.; Mauriz, Paulo Wilson; Vasconcelos, Manoel Silva de; Caetano, E. W. S.; Freire, V. N.; Albuquerque, Eudenilson Lins de; Fulco, Umberto LaicoWe present an in silico study of the interaction energy between NS2B–NS3, a serine protease of the dengue virus (DENV), and the inhibitor benzoyl-norleucine-Lys-Arg-Arg-aldehyde (Bz-nKRR-H), a crucial step in the design and development of dengue's antiviral drugs, using quantum chemistry calculations based on the density functional theory (DFT) at the generalized gradient approximation (GGA). The interaction energies between the inhibitor Bz-nKRR-H and each amino acid belonging to the binding site was calculated through the molecular fragmentation with conjugate caps (MFCC) approach employing a dispersion corrected exchange-correlation functional. Besides the interaction energy, we also calculated the distances, types of molecular interactions, and the atomic groups involved in the process. Our results show that the interaction energy of the system reached convergence at 15.0 Å, with the central residues identified in this interaction radius, as well as their attraction/repulsion energies, all of them being important inputs to improve the effectiveness of antiviral drugs to avoid the dissemination of the dengue virusArtigo Structural, electronic and optical properties of ilmenite and perovskite CdSnO3 from DFT calculations(IOP Publishing, 2010-10-12) Sesion Junior, Paulo Dantas; Henriques, J. M.; Barboza, C. A.; Albuquerque, E. L.; Freire, V. N.; Caetano, E. W. S.CdSnO3 ilmenite and perovskite crystals were investigated using both the local density and generalized gradient approximations, LDA and GGA, respectively, of the density functional theory (DFT). The electronic band structures, densities of states, dielectric functions, optical absorption and reflectivity spectra related to electronic transitions were obtained, as well as the infrared absorption spectra after computing the vibrational modes of the crystals at q = 0. Dielectric optical permittivities and polarizabilities at ω = 0 and ∞ were also calculated. The results show that GGA-optimized geometries are more accurate than LDA ones, and the Kohn–Sham band structures obtained for the CdSnO3 polymorphs confirm that ilmenite has an indirect band gap, while perovskite has a direct band gap, both being semiconductors. Effective masses for both crystals are obtained for the first time, being highly isotropic for electrons and anisotropic for holes. The optical properties reveal a very small degree of anisotropy of both crystals with respect to different polarization planes of incident light. The phonon calculation at q = 0 for perovskite CdSnO3 does not show any imaginary frequencies, in contrast to a previous report suggesting the existence of a more stable crystal of perovskite CdSnO3 with ferroelectric properties