Navegando por Autor "Ramalho, Teodorico de Castro"
Agora exibindo 1 - 13 de 13
Resultados por página
Opções de Ordenação
Item 99Tc NMR as a promising technique for structural investigation of biomolecules : theoretical studies on the solvent and thermal effects of phenylbenzothiazole complex.(2014) Mancini, Daiana Teixeira; Souza, Eugenio F.; Caetano, Melissa Soares; Ramalho, Teodorico de CastroThe phenylbenzothiazole compounds show antitumor properties and are highly selective. In this paper, the 99Tc chemical shifts based on the (99mTc)(CO)3(NNO) complex conjugated to the antitumor agent 2-(4′-aminophenyl)benzothiazole are reported. Thermal and solvent effects were studied computationally by quantum-chemical methods, using the density functional theory (DFT) (DFT level BPW91/aug-cc-pVTZ for the Tc and BPW91/IGLO-II for the other atoms) to compute the NMR parameters for the complex. We have calculated the 99Tc NMR chemical shifts of the complex in gas phase and solution using different solvation models (polarizable continuum model and explicit solvation). To evaluate the thermal effect, molecular dynamics simulations were carried, using the atom-centered density matrix propagation method at the DFT level (BP86/ LanL2dz). The results highlight that the 99Tc NMR spectroscopy can be a promising technique for structural investigation of biomolecules, at the molecular level, in different environments.Item Adsorption of diclofenac on a magnetic adsorbent based on maghemite : experimental and theoretical studies.(2018) Leone, Victor Oliveira; Pereira, Márcio César; Aquino, Sergio Francisco de; Oliveira, Luiz Carlos Alves de; Corrêa, Silviana; Ramalho, Teodorico de Castro; Gurgel, Leandro Vinícius Alves; Silva, Adilson Cândido daIn the present study, a magnetic adsorbent for diclofenac formed by maghemite (g-Fe2O3) nanoparticles with high saturation magnetization (19.8 emu g 1) and specific area (79 m2 g 1) was synthesized by a one-pot method through the precipitation of Fe2+ ions with NaOH solution followed by rapid oxidation with hydrogen peroxide. The X-ray diffraction and Mo¨ssbauer spectroscopy data confirmed that the adsorbent is formed solely by maghemite. The adsorption equilibrium time for diclofenac (C0 = 500 mg L 1) was reached after 120 min, and the kinetic data were best fitted to the pseudo-first-order model. The adsorption isotherms acquired at five different temperatures showed an increase in the maximum adsorption capacity (261 mg g 1) until 298 K, but at higher temperatures, the maximum adsorption capacity was not increased. The isotherm data were best fitted to the Langmuir and Sips models. Adsorption tests as a function of solution pH showed a decrease in the diclofenac adsorption capacity with increasing solution pH, suggesting that the hydroxyl anions compete with diclofenac molecules for the adsorption sites. Diclofenac adsorption on maghemite was endothermic (67.31 kJ mol 1) and entropically driven (TDadsS1 = 96.33 kJ mol 1). Finally, theoretical calculations and infrared spectroscopy data suggest a physisorption mechanism of diclofenac on the maghemite surface.Item Bonding, structure, and stability of [(Na)𝑛(Phe)𝑚]𝑛+ clusters : some surprising results from an experimental and theoretical investigation in gas phase.(2013) Caetano, Melissa Soares; Ramalho, Teodorico de Castro; Vieira, Tales Giuliano; Gonçalves, Arlan da Silva; Mancini, Daiana Teixeira; Cunha, Elaine Fontes Ferreira daStructure and stability of [(Na) 𝑛 (Phe)𝑚]𝑛+ clusters in the ground state were analyzed at the theoretical and experimental levels. Our experimental and theoretical findings showed that the [(Na) 𝑛 (Phe)𝑚]𝑛+ clusters in gas phase tend to form mainly planar rings of four members. The symmetry and the small dipole moment in these specific configurations suggested that their stability could be associated with an alignment of the water molecules, maximizing attractive electrostatic interactions caused by changes in the charge distribution of the clusters.Item Desenvolvimento de catalisadores nanoestruturados para obtenção de produtos de interesse comercial via processos de oxidação do tioanisol em fase líquida.(2022) Teixeira, Moisés Paulo; Fajardo, Humberto Vieira; Fajardo, Humberto Vieira; Ramalho, Teodorico de Castro; Silva, Anderson Gabriel Marques da; Carreño, Neftalí Lenin Villarreal; Silva, Adilson Cândido daA catálise está presente em pelo menos uma das etapas da maioria dos processos industriais. A literatura científica está repleta de estudos que envolvem o desenvolvimento de materiais para aplicações catalíticas, buscando obtê-los com custo reduzido, que sejam ativos, seletivos, estáveis frente às reações catalisadas e de preferência ambientalmente amigáveis. Com os avanços da pesquisa, é possível produzir materiais nanoestruturados de diversas morfologias. Estes materiais têm demonstrado maiores atividades catalíticas em comparação com os sólidos estendidos. O objetivo desse projeto é desenvolver catalisadores heterogêneos em escala nanométrica, sintetizados por diferentes rotas, visando a aplicação na reação de oxidação do tioanisol, em fase líquida, para obtenção de produtos de interesse industrial. Foram preparados, como catalisadores, nanofios de CeO2 e nanofios de CeO2 decorados com nanopartículas de ouro (Au-CeO2#nw), além de materiais análogos obtidos a partir do CeO2 comercial. Utilizou- se o método hidrotérmico para a preparação dos materiais. Observou-se que os nanofios de Au- CeO2, apresentaram desempenhos catalíticos significativamente melhores comparativamente aos demais catalisadores. Pôde ser alcançada conversão de até 90% sobre esse catalisador, com 100% de seletividade para metil fenil sulfóxido. Preparou-se, também, catalisadores à base de titanato de estrôncio (STO) e titanato de estrôncio recoberto com óxido de nióbio (STO/Nb2O5) por dois métodos: método Pechini e método hidrotérmico assistido por micro-ondas (MHAM). O catalisador STO/Nb2O5 demonstrou maior atividade catalítica para essas reações quando comparado ao STO puro, alcançando 100% de conversão do reagente e 100% de seletividade para metil fenil sulfona. Por fim, foram preparados catalisadores de sílica sintética (SiO2), sílica dopada com 5% de nióbio (Nb5%SiO2) e sílica dopada com 10% de nióbio (Nb10%SiO2). Os catalisadores com nióbio foram obtidos a partir da impregnação da SiO2 com uma solução de oxalato amoniacal de nióbio. A presença do nióbio na matriz impulsionou a atividade catalítica, atingindo-se 88% de conversão sobre o catalisador (Nb10%SiO2). De um modo geral, os catalisadores preparados durante essa pesquisa demonstraram desempenhos equiparáveis e, em alguns casos, superiores àqueles apresentados por catalisadores relatados na literatura. Cabe ressaltar também que os resultados obtidos nesse estudo, através da utilização de catalisadores heterogêneos associados a um agente oxidante ambientalmente amigável, como o peróxido de hidrogênio, em condições reacionais relativamente brandas, podem se tornar economicamente atrativos, satisfazendo os ideais da química verde.Item Electrocatalytic performance of different cobalt molybdate structures for water oxidation in alkaline media.(2018) Rodriguez, Mariandry del Valle Rodriguez; Stolzemburg, Matheus Cata Preta; Bruziquesi, Carlos Giovani Oliveira; Silva, Adilson Cândido da; Abreu, Cíntia Grossi de; Siqueira, Kisla Prislen Félix; Oliveira, Luiz Carlos Alves de; Pires, Maíra dos Santos; Lacerda, Lívia Clara Tavares; Ramalho, Teodorico de Castro; Dias, Anderson; Pereira, Márcio CésarCobalt molybdates with different crystalline structures, i.e., α, β, and hydrated (H)-CoMoO4, were synthesized, and their electrocatalytic activities were thoroughly examined for catalyzing the oxygen evolution reaction (OER) in alkaline media. The material characteristics were associated with the electrocatalytic properties by evaluating the CoMoO4 crystal structures (XRD and Raman), morphologies (TEM), and electrochemical features (electrochemically active surface area, roughness factor, electrochemical impedance, Tafel analysis, and controlled-current electrolysis). These combined findings revealed that the electrocatalytic performance is greatly influenced by the crystalline structures of CoMoO4, following the order α-CoMoO4 > H-CoMoO4 > β-CoMoO4. The H-CoMoO4 catalysts crystallized in the triclinic space group, P[1 with combining macron] (#2), with Z = 4. On the other hand, the α- and β-CoMoO4 catalysts exhibited a monoclinic structure, C2/m (#12), with Z = 8. In the OER experiments, α-CoMoO4 showed an overpotential of 0.43 ± 0.05 V compared to the 0.51 ± 0.05 V and 0.56 ± 0.04 V exhibited by the H-CoMoO4 and β-CoMoO4 catalysts, respectively, to achieve 10 mA cm−2. All CoMoO4 structures displayed stability for at least 6 h at a controlled current density of 10 mA cm−2. Finally, computational simulations indicate that the coexistence of Co and Mo ions in edge-shared octahedral sites of α-CoMoO4 may favor the interaction between the O atom of the water molecule and the metal adsorption sites due to its surface being electronically less dense than β- and H-CoMoO4 surfaces, thus resulting in its higher performance for OER.Item Experimental and theoretical studies of solvent polarity influence on the preparation of molecularly imprinted polymers for the removal of estradiol from water.(2019) Xavier, Leandro Pablo dos Santos; Dias, Ana Carolina; Baeta, Bruno Eduardo Lobo; Santos, Lucas de Azevedo; Ramalho, Teodorico de Castro; Aquino, Sergio Francisco de; Silva, Adilson Cândido daThe aim of this work was to study the synthesis of molecularly imprinted polymers (MIPs) for the selective adsorption of b-estradiol (E2). For this, six solvents with different polarities were tested and the results indicated that, for obtaining a good E2 adsorbent, the solvent should be moderately polar to favor the formation of a monomer–template complex during the synthesis. Synthesis with acetonitrile (ACN) or a mixture of chloroform (CFM) and dimethylsulfoxide (DMSO) 1 : 1 led to higher E2 adsorption capacities (from 26 to 37 mg g1). The use of MIP-CFM:DMSO resulted in better results than that of MIP-ACN relative to their NIPs (about 3 times more for CFM:DMSO, compared to 1.5 times for ACN) for the adsorption capacities. This can be explained by the fact that ACN is a porogen solvent, which on one hand increased the area of the adsorbent material but on the other reduced its selectivity towards E2 adsorption.Item Molecular insight into the inhibition mechanism of plant and rat 4-hydroxyphenylpyruvate dioxygenase by molecular docking and DFT calculations.(2015) Silva, Telles Cardoso; Pires, Maíra dos Santos; Castro, Alexandre Alves de; Cunha, Elaine Fontes Ferreira da; Caetano, Melissa Soares; Ramalho, Teodorico de CastroThe 4-hydroxyphenylpyruvate dioxygenase (HPPD) is a relevant target protein for therapeutic and agrochemical research. It is an iron-dependent enzyme, and its inhibition has very different effects on plants and animals. In animals, the enzyme has an important role in the catabolism of tyrosine, and in the plant, it operates in the cascade of photosynthesis. Potent HPPD inhibitors have been described, and all contain the 1,3-diketone group in its shape. In this research, we carried out a study of the interaction modes of HPPD enzymes from plant and rat with selective and non-selective herbicides which already available with their structures to identify the molecule groups which are essential to their activity and those that are likely to changes, mediated by molecular computations. In this theoretical investigation, methods of molecular docking, reaction mechanism (QM/MM) and AIM calculations were employed, aiming the search for new more active and selective herbicides. Modifications were performed for DAS 645 and DAS 869 inhibitors. DAS 645 presented a good selectivity for the inhibition of the plant enzyme, and the modifications to the analogs design done increased its activity. For this compound, p–p* stacking interactions seem to be important, and this fact was proven by using AIM calculations. The other prototype compound, DAS 869, a potent inhibitor for both enzymes, had its increased activity in the plant and rat enzyme after added groups capable of performing p–p* stacking interactions.Item Molecularly imprinted polymers for selective adsorption of quinoline : theoretical and experimental studies.(2018) Martínez Saavedra, Liz Nayibe; Penido, Ricardo Gonçalves; Santos, Lucas de Azevedo; Ramalho, Teodorico de Castro; Baeta, Bruno Eduardo Lobo; Pereira, Márcio César; Silva, Adilson Cândido daThe effects of solvent on the synthesis of molecularly imprinted polymers (MIPs) for the selective adsorption of quinoline were evaluated in this work. The MIPs were synthesized by the “bulk” method using the quinoline molecule (IQ) as a template in different solvents, such as toluene (MIPT) and chloroform (MIPC). The adsorbents were characterized by thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and N2 adsorption/desorption measurements. The influences of time, adsorbate concentration, and temperature on the adsorption of quinoline by MIPT and MIPC were evaluated. Maximum adsorption capacities (qe) of 35.23 and 24.10 mg g−1 were obtained for MIPT and MIPC, respectively. Thermodynamic studies indicate that occur physisorption and a spontaneous process (ΔadsG° < 0) entropically directed. Finally, the highest selectivity and reusability of MIPC for quinoline adsorption was ascribed to the better interaction between the chloroform and monomer, which favors the formation of porous adsorbents with higher numbers of adsorption sites.Item Planejamento computacional, síntese e ensaio biológico de novos potenciais agentes anticâncer tendo como alvo enzima FoxM1.(2017) Araújo, Bárbara Caroline Rodrigues de; Taylor, Jason Guy; Caetano, Melissa Soares; Taylor, Jason Guy; Ramalho, Teodorico de Castro; Santos, Viviane Martins Rebello dosA genisteína e a quercetina são as isoflavonas presentes em maiores quantidades e com maior atividade biológica em uma dieta à base de soja. A genisteína tem propriedades anticancerígenas e possui uma capacidade de induzir a morte celular através da apoptose e também pela autofagia. Em estudos in vitro e in vivo a genisteína mostrou um efeito protetor na carcinogênese, quando usada sozinha ou em combinação com outros compostos. A quercetina, um bioflavonoide cuja ingestão é estimada individualmente por 25 mg por dia, pode ser encontrado em vários alimentos como frutas e vegetais. Estudos têm demonstrado que a molécula atua em diversas funções no organismo e diferentes linhagens celulares, contribuindo para a inibição do câncer. A genisteína e quercetina atuam como potentes agentes anticancerígenos através da interação com as enzimas FoxM1 e FoxO1, respectivamente. As enzimas da família Fox são fatores de transcrição importantes na divisão celular e sua alta expressão está relacionada ao crescimento de células cancerígenas. A obtenção de informações sobre as interações ligante-receptor para a descoberta de potenciais novos fármacos tem atraído cada vez mais o interesse da comunidade científica e das empresas. Este trabalho tem por objetivo trazer um impacto positivo na busca de informações sobre possíveis novos medicamentos anticancerígenos. A partir dos resultados da modelagem molecular foram obtidos derivados de genisteína e quercetina que apresentaram melhor interação com enzima alvo sendo candidatos a potenciais a novos fármacos: mais um passo para a luta contra o câncer. Três dos análogos da quercetina foram sintetizados, caracterizados por RMN, IV, espectrometria de massas e passaram por teste biológico de viabilidade celular, mostrando não serem tóxicos para célula.Item Removal of sodium diclofenac from aqueous medium using layered double hydroxide : a thermodynamic and theoretical approach.(2022) Bruziquesi, Carlos Giovani Oliveira; Xavier, Farlon Felipe Silva; Pacheco, Ingrid da Silva; Amaral, Fábio Augusto do; Canobre, Sheila Cristina; Gonçalves, Mateus A.; Ramalho, Teodorico de Castro; Martínez Saavedra, Liz Nayibe; Gurgel, Leandro Vinícius Alves; Silva, Adilson Cândido daIn this study, an adsorbent based on layered double hydroxide (Co–Al–NO3]-LDH) was synthesized by the co-precipitation method at constant pH 8.0±0.5. This new material was used for the removal of diclofenac from water. The X-ray difraction pattern of [Co–Al–NO3]-LDH revealed a basal spacing of 0.859 nm. Equilibrium time was reached after 120 min for an initial concentration (C0) of diclofenac of 500 mg L−1, and the pseudo-second order model best ftted the kinetic data obtained at C0 values of 100, 250, and 500 mg L−1. The isotherms performed at 15, 25, 35, and 45 °C showed an increase in the maximum adsorption capacity (Qmax=494.9 mg g−1) up to 25 °C, but at temperatures above 25 ºC, the Qmax value was not increased. Equilibrium data were ftted using the Langmuir, Freundlich, and Sips models, and the change in standard free energy of adsorption was estimated from the Langmuir constant, corrected for the equilibrium activity coefcient, while the changes in standard enthalpy and entropy of adsorption were calculated from the van’t Hof equation. Adsorption studies as a function of nitrate concentration at two C0 values (50 and 500 mg L−1) showed that the increase in nitrate concentration led to a decrease in the Qmax of diclofenac, showing that nitrate competes with diclofenac for the adsorption sites. Theoretical studies were carried out using four diferent confgurations of the diclofenac molecule approaching the surface of [Co–Al–NO3]-LDH. The interaction distance between diclofenac and [Co–Al–NO3]-LDH of 2.0 Å presented the lowest energy.Item Synthesis, structural characterization, and thermalproperties of the poly (methylmethacrylate) / 𝛿 FeOOH hybrid material : an experimental and theoretical study.(2016) Corrêa, Silviana; Lacerda, Lívia Clara Tavares; Santos, Maíra dos Santos; Rocha, Marcus Vinícius Juliaci; Nogueira, Francisco Guilherme Esteves; Silva, Adilson Cândido da; Pereira, Márcio César; Brito, Angela Dayana Barrera de; Cunha, Elaine Fontes Ferreira da; Ramalho, Teodorico de CastroThe 𝛿-FeOOH/PMMA nanocomposites with 0.5 and 2.5 wt.% of 𝛿-FeOOH were prepared by grafting 3 (trimethoxysilyl)propyl methacrylate on the surface of the iron oxyhydroxide particles.TheFTIR spectra of the 𝛿-FeOOH/PMMA nanocomposites showed that the silanemonomers were covalently attached to the 𝛿 FeOOHparticles. Because of the strong interaction between the PMMA and 𝛿-FeOOH nanoparticles, the thermal stability of the 𝛿-FeOOH/PMMA nanocomposites was improved compared to the pure PMMA.The SEM analysis conferred the size agglomerate of particles regarding the morphology of samples.The theoretical study enabled a better understanding of the interaction of the polymer with the iron oxyhydroxide.The DFT-based calculations reinforce the radical trapping mechanism of stabilization of nanocomposites; that is, Fe3+ species might be able to accept electrons coming from the organic phase that decomposes via radical unzipping.The radical scavenge effect delays the weight loss of polymer.Item Thioanisole oxidation promoted by new niobium-based catalyst : the effect of surface hydroxyl groups on catalytic performance.(2023) Aguiar, Guilherme Carletti de; Batalha, Daniel Carreira; Fajardo, Humberto Vieira; Gabriel Filho, José Balena; Bruziquesi, Carlos Giovani Oliveira; Oliveira, Luiz Carlos Alves de; Gonçalves, Mateus Aquino; Ramalho, Teodorico de Castro; Silva, Adilson Cândido daIn this work, the application of a new, synthesized niobium-based catalyst, called S4 (niobium oxyhydroxide), in the liquid-phase oxidation of methyl-phenyl sulfide (thioanisole) using hydrogen peroxide as oxidant was proposed. The synthetic method employed provided a material with low crystallinity and high specific surface area and acidity. A commercial material, called HY-340 (hydrated niobium oxide), was also employed as heterogeneous catalyst for comparative purposes. The results showed that the synthesized S4 material is an outstanding catalyst, being able to completely convert the substrate (thioanisole) that achieves almost 90% of selectivity for methyl phenyl sulfone formation, under mild reaction conditions. According to the theoretical and experimental combined results, the superior performance of S4 catalyst is related to the better interaction of H2O2 and thioanisole molecules with S4 surface, compared to HY-340, pointing to the greater ability of this catalyst to form reactive oxygen species in contact with hydrogen peroxide, due to its higher content of free hydroxyl groups present on its surface.Item Xylose dehydration to furfural using niobium doped δ-FeOOH as catalyst.(2022) Campos, Paulo Tadashi Bannai; Bonesio, Mariana de Rezende; Lima, André Luiz Dias; Silva, Adilson Cândido da; Mancini, Daiana Teixeira; Ramalho, Teodorico de CastroThe effect of modification of δ-FeOOH with niobium, applied to dehydration reaction of xylose, was evaluated by experimental and theoretical methods. The experimental data confirmed, namely the characteristic peaks in the X-ray diffractometer analysis, that the materials were obtained. Inductively coupled plasma mass spectrometry analysis defined the percentage of Nb as 0 for pure δ-FeOOH and 9.5 wt. % (δ-FeOOH/Nb) for doped. In relation to obtaining furfural, the doped material presents a conversion improvement of 290 % when compared to pure catalyst. Theoretical calculations were useful in understanding the preferential route of the mechanisms proposed by the obtained potential energy values. To understand the preferred routes, the most favorable position of xylose in relation to δ-FeOOH was initially calculated. From this, the conditions favoring furfural formation were calculated based on the routes of the proposed mechanisms and the energy values indicated that the furfural formation is more likely to happen on the doped material.