Doutorado em Física (IF)
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Item Variação da energia livre na hidratação de séries homólogas de poliol, glicina e peptídeos ANK usando modelos contínuo e discreto de solvente(Universidade Federal de Goiás, 2017-05-12) Abreu, Leonardo Martins de; Fileti, Eudes Eterno; http://lattes.cnpq.br/5294929829300325; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca, Tertius Lima da; Moreno, Roberto Rivelino de Melo; Fujimoto , Milton Massumi; Vale, Renato Pessoa; Silva, Ladir Cândido daUsing continuum and discrete solvent description models, we have investigated the chain length dependence of hydration free energy of polyol, glycine and ANK peptides. In this work this property values were calculated using thermodynamics integration with classical molecular dynamics simulation of one solute molecule to around 1000 solvent molecules. In addition, hydration free energy of polyol, glycine and ANK peptides were also calculated using polarizable continuum model in combination with the universal solvation model. Dipole moment and linear polarizability of the three systems had been also calculate using the PCM method. Our MD results show that ΔG exhibit a linear pattern with the size of glycine and ANK chain as well as observed for organic compounds in literature. In opposition, polyol’s ΔG shows a nonlinear behavior with increasing chain length and for this group of molecules it were found that water solvating effects have an important role over the polyol’s electric properties. These results suggest that in the case of polyols not only variation of polarizability but also variations of dipole moment in going from vacuum to water can influence the behavior of the free energy of hydration. All DM and PCM calculations were performed using the GROMACS 4.5 and the GAUSSIAN09 programs, respectively.Item Estudo teórico de propriedades espectroscópicas de bases nitrogenadas e derivados de vitamina A em solução(Universidade Federal de Goiás, 2012-03-23) Oliveira, Guilherme Colherinhas de; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca , Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Moreno, Roberto Rivelino de Melo; Stassen, Hubert Karl; Maia, Lauro June Queiroz; Osório, Francisco Aparecido PintoIn this work we present a theoretical study for the optical absorption spectrum UV-VIS and nuclear magnetic resonance (NMR) parameters of molecules that forming the structure of the deoxyribonucleic acid (DNA): adenine, guanine, thymine and cytosine in aqueous solution and of aldehydes and carboxylic acids derivatives of vitamin A in solution of chloroform, acetonitrile, methanol and water. The Solvent effects are treated using a sequential methodology that combines Monte Carlo simulation and quantum mechanics calculations (S-MC / MQ). Effects of polarization of the reference molecules by the solvent are obtained iteratively assuring the convergence of the dipole moment in solution, with the atoms of the solvent molecules modeled by point charges. The results show that the polarization effect can give marked increases for the dipole moments of the reference molecules, especially in water, as compared with the results of gas phase. TD-DFT calculations for the vertical electronic transitions were performed with hybrid functionalities: B3LYP, PBE1PBE and BHandHLYP; and with long-range corrected functionals: CAM-B3LYP and LC-wPBE. For the isotropic magnetic shielding constants, GIAO-B3LYP results were obtained with several basis set functions: 6-311 ++ G (2d, 2p), AUG-cc-pVTZ, pcS-2, pcS-3 and AUG-pcS -2. The results obtained show the optical absorption spectrum variations between 6 and 28 nm for the nucleotide bases and between 13 and 80 nm for the derivatives of vitamin A with the functional type, whereas that for the NMR parameters of carbon atoms variations between 3 and 10 ppm with the choice of the basis set functions. However, the inclusion of the solvent polarization effects provides a reliable description for these electronic properties in solution, in comparison with available experimental results. The classical simulations were performed with the DICE program and the quantum calculations with the GAUSSIAN03 / 09 program.Item Propriedades estruturais e espectroscópicas de modelos de vitamina E e de constituintes da eumelanina em água e em mistura de solventes(Universidade Federal de Goiás, 2015-10-02) Oliveira, Leonardo Bruno Assis; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca , Tertius Lima da; Canuto, Sylvio Roberto Accioly; Custodio, Rogério; Georg, Herbert de Castro; Osório, Francisco Aparecido PintoWe present in this work a theoretical study of structural and spectroscopic properties of vitamin E models in chloroform and water solutions, of eumelanin oligomers in water and also of eumelanin constituents in mixtures of methanol and water. The in uence of solvent e ects in molecular properties was included using an iterative process based on sequential methodology Monte Carlo/Quantum Mechanics. Optical absorption spectra were obtained from TD-DFT calculations with B3LYP, PBE1PBE, BHandHLYP and CAMB3LYP functionals whereas the magnetic shielding constants were calculated employing the gauge-including atomic orbital (GIAO) approach through B3LYP functional. We analyze four homologous forms of vitamin E models, which di er in the number and position of methyl groups on the chromanol ring. The inclusion of solvent e ects in the rst electronic transition indicates solvatochromic shifts ranging between 1 and 3 nm in chloroform, and between 7 and 11 nm in water. The results also show that these e ects on the magnetic shielding constants (13C) and (17O) are small, but an appropriate description of the solvent shift for (17O) of the hydroxyl group in water requires the inclusion of explicit molecules that make hydrogen bonds. Our results for the chemical shifts (13C) of the carbon atoms of the chromanol ring in chloroform solution are in good agreement with the experimental results, although overestimated between 3 and 9 ppm. The analysis of the con gurations obtained from Monte Carlo simulations shows that for eumelanin oligomers of increasing size, monomers, dimers, tetramers and a layer, there is an increase in the average total number of hydrogen bonds. Solvent e ects are particularly relevant for the NMR spectroscopy of nitrogen and oxygen atoms. The shielding constant (17O) may change up to 98% for the monomers, when we consider the presence of explicit water molecules, and up to 41% for the tetramers from calculations with ASEC (Average Solvent Eletrostatic Con guration). In general, the oligomerization of eumelanin constituents extends the region of the electromagnetic spectrum which occurs the optical absorption and also shows a shift of the absorption peak of the HOMO!LUMO transitions for longer wavelength regions. We also present a superposition of the absorption spectra of eumelanin constituents that shows the trend of experimental results. We select some eumelanin constituents to analyze the e ects of mixtures of methanol and water on the spectroscopic properties. The results indicate that the concentration of water in the mixture can in uence the magnetic shielding constants of more electronegative atoms, as well as the position of the absorption spectrum peaks. The results show that the values of can present variations up to 34% while the location of the absorption peak can change up to 73 nm in going from pure methanol to pure water. We also analyze the distribution of the methanol and water molecules around the eumelanin constituents studied in order to determine the preferential solvation.Item Estudo teórico de (hiper) polarizabilidades de cristais orgânicos(Universidade Federal de Goiás, 2016-10-27) Santos, Orlei Luiz dos; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Fonseca, Tertius Lima da; http://lattes.cnpq.br/8193800922148980; Gargano, Ricardo; Martins, João Batista Lopes; Silva, Ladir Cândido da; Souza, Márcio Adriano RodriguesThis work presents the results for the dipole moment and the static (hyper)polarizabilities of urea, thiourea and 3-methyl-4-nitropyridine-1-oxyde crystals under the influence of the crystalline environment. We have used the approach of Hartree-Fock together with Moller- Plesset theory of second order to include the effects of electron correlation in the electrical properties of the compounds. These properties were calculated using the numerical method of finite field. The polarization effects were included using an iterative electrostatic process where the neighboring molecules to the reference compound are treated as point charges. All compounds were found to be very sensitive to environmental effects, especially with regard to the dipole moment and the first hyperpolarizability. The linear polarizability presented values embedded with insignificant variations in relation to isolated results. However, in all of the compounds, it showed an additive behavior. Additionally, it was possible to estimate values for the macroscopic electrical properties and verify a reasonable agreement with other theoretical and/or experimental results.