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Search Results: 1 - 10 of 430156 matches for " Davi S. B. Brasil "
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Application of Hartree-Fock Method for Modeling of Bioactive Molecules Using SAR and QSPR  [PDF]
Cleydson B. R. Santos, Cleison C. Lobato, Francinaldo S. Braga, Sílvia S. S. Morais, Cesar F. Santos, Caio P. Fernandes, Davi S. B. Brasil, Lorane I. S. Hage-Melim, Williams J. C. Macêdo, José C. T. Carvalho
Computational Molecular Bioscience (CMB) , 2014, DOI: 10.4236/cmb.2014.41001
Abstract:
The central importance of quantum chemistry is to obtain solutions of the Schr?dinger equation for the accurate determination of the properties of atomic and molecular systems that occurred from the calculation of wave functions accurate for many diatomic and polyatomic molecules, using Self Consistent Field method (SCF). The application of quantum chemical methods in the study and planning of bioactive compounds has become a common practice nowadays. From the point of view of planning it is important to note, when it comes to the use of molecular modeling, a collective term that refers to methods and theoretical modeling and computational techniques to mimic the behavior of molecules, not intend to reach a bioactive molecule simply through the use of computer programs. The choice of method for energy minimization depends on factors related to the size of the molecule, parameters of availability, stored data and computational resources. Molecular models generated by the computer are the result of mathematical equations that estimate the positions and properties of the electrons and nuclei, the calculations exploit experimentally, the characteristics of a structure, providing a new perspective on the molecule. In this work we show that studies of Highest Occupied Molecular Orbital Energy (HOMO), Low Unoccupied Molecular Orbital Energy (LUMO) and Map of molecular electrostatic potential (MEP) using Hatree-Fock method with different basis sets (HF/3-21G*, HF/3-21G**, HF/6-31G, HF/6-31G*, HF/6-31G** and HF/6-311G), that are of great importance in modern chemistry, biochemistry, molecular biology, and other fields of knowledge of health sciences. In order to obtain a significant correlation, it is essential that the descriptors are used appropriately. Thus, the quantum chemical calculations are an attractive source of new molecular descriptors that can, in principle, express all the geometrical and electronic properties of molecules and their interactions with biological receptor.
Evaluation of Quantum Chemical Methods and Basis Sets Applied in the Molecular Modeling of Artemisinin  [PDF]
Cleydson B. R. dos Santos, Cleison C. Lobato, Josinete B. Vieira, Davi S. B. Brasil, Alaan U. Brito, Williams J. C. Macêdo, José Carlos T. Carvalho, José C. Pinheiro
Computational Molecular Bioscience (CMB) , 2013, DOI: 10.4236/cmb.2013.33009
Abstract: In this paper, we evaluate semiempirical methods (AM1, PM3, and ZINDO), HF and DFT (B3LYP) in different basis sets to determine which method best describes the sign and magnitude of the geometrical parameters of artemisinin in the region of the endoperoxide ring compared to crystallographic data. We also classify these methods using statistical analysis. The results of PCA were based on three main components, explaining 98.0539% of the total variance, for the geometrical parameters C3O13, O1O2C3, O13C12C12a, and O2C3O13C12. The DFT method (B3LYP) corresponded well with the experimental data in the hierarchical cluster analysis (HCA). The experimental and theoretical angles were analyzed by simple linear regression, and statistical parameters (correlation coefficients, significance, and predictability) were evaluated to determine the accuracy of the calculations. The statistical analysis exhibited a good correlation and high predictive power for the DFT (B3LYP) method in the 6-31G** basis set.
Isolation, X-ray crystal structure and theoretical calculations of the new compound 8-Eepicordatin and identification of others terpenes and steroids from the bark and leaves of Croton palanostigma Klotzsch
Brasil, Davi S. B.;Müller, Adolfo H.;Guilhon, Gisele M. S. P.;Alves, Cláudio N.;Peris, Gabriel;Llusar, Rosa;Moliner, Vicent;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000400021
Abstract: phytochemical studies of the bark and leaves of croton palanostigma klotzsch (euphorbiaceae) led to the isolation of a new clerodane diterpene, 8-epicordatin (2), in addition to 12-oxohardwickiic acid methyl ester (3), aparisthman, cordatin (1), ent-trachyloban-18-oic acid, ent-13-epimanoyl oxide, ent-3-oxo-13-epimanoyl oxide, ent-3β-hydroxy-13-epimanoyl oxide, sitosterol, stigmasterol, stigmastan-3-one, 6β-hydroxystigmast-4-en-3-one, 6β-hydroxystigmasta-4,22-dien-3-one, stigmast-4-en-3-one, stigmasta-4,22-dien-3-one, 3-o-acetylaleuritolic acid, 11α-hydroxyurs-12-en-3-one, α-amyrenone, 24-methylenecycloartenone and lupenone. these compounds were isolated using typical phytochemical procedures and the structures were deduced from spectroscopic studies, including 2d nmr experiments. in addition, the crystalline structure of 8-epicordatin (2) was determined by x-ray diffraction. nmr theoretical calculations at the b3pw91/dgdzvp level were used to confirm the assignment of the chemical shifts of the h-7α and h-7β hydrogens of 8-epicordatin.
Volatiles, A Glutarimide Alkaloid and Antimicrobial Effects of Croton pullei (Euphorbiaceae)
Rosana N. S. Peixoto,Giselle M. S. P. Guilhon,Maria das Gra?as B. Zoghbi,Isabella S. Araújo,Ana Paula T. Uetanabaro,Lourivaldo S. Santos,Davi do S. B. Brasil
Molecules , 2013, DOI: 10.3390/molecules18033195
Abstract: Chemical investigation of Croton pullei (Euphorbiaceae) collected in the Brazilian Amazon region was revisited. The chemical composition of the essential oils of leaves and stems was analyzed by GC/MS. It was found that both the oils comprise mainly terpenes, among which linalool was the major one (24.90 and 39.72%, respectively). Phytochemical investigation of the stem methanol extract led to the isolation of a new natural product from the glutarimide alkaloid group named N-[2,6-dioxo-1-(2-phenylethyl)-3-piperidinyl]-acetamide, confirming that C. pullei is a rich source of this class of alkaloids. The hexane and methanol extracts of the stems of C. pullei showed moderate antibacterial and antifungal activity and the highest inhibition was observed when the methanol extract was tested against Staphylococcus aureus CCMB 262 and CCMB 263.
A SAR and QSAR Study of New Artemisinin Compounds with Antimalarial Activity
Cleydson Breno R. Santos,Josinete B. Vieira,Cleison C. Lobato,Lorane I. S. Hage-Melim,Raimundo N. P. Souto,Clarissa S. Lima,Elizabeth V. M. Costa,Davi S. B. Brasil,Williams Jorge C. Macêdo,José Carlos T. Carvalho
Molecules , 2014, DOI: 10.3390/molecules19010367
Abstract: The Hartree-Fock method and the 6-31G** basis set were employed to calculate the molecular properties of artemisinin and 20 derivatives with antimalarial activity. Maps of molecular electrostatic potential (MEPs) and molecular docking were used to investigate the interaction between ligands and the receptor (heme). Principal component analysis and hierarchical cluster analysis were employed to select the most important descriptors related to activity. The correlation between biological activity and molecular properties was obtained using the partial least squares and principal component regression methods. The regression PLS and PCR models built in this study were also used to predict the antimalarial activity of 30 new artemisinin compounds with unknown activity. The models obtained showed not only statistical significance but also predictive ability. The significant molecular descriptors related to the compounds with antimalarial activity were the hydration energy (HE), the charge on the O11 oxygen atom (QO11), the torsion angle O1-O2-Fe-N2 (D2) and the maximum rate of R/Sanderson Electronegativity (RTe +). These variables led to a physical and structural explanation of the molecular properties that should be selected for when designing new ligands to be used as antimalarial agents.
Identification of (?)(E)-N-[2(S)-Hydroxy-2-(4-hydroxyphenyl) ethyl]ferulamide, a Natural Product Isolated from Croton Pullei: Theoretical and Experimental Analysis
Silvana de O. Silva,Rosana N.S. Peixoto,José Rogério A. Silva,Cláudio N. Alves,Giselle M.S.P. Guilhon,Lourivaldo S. Santos,Davi do S.B. Brasil
International Journal of Molecular Sciences , 2011, DOI: 10.3390/ijms12129389
Abstract: Ferulic acid (FA) and its derivatives (FADs) are known for a variety of biological activities, such as photo-protective agent, antioxidant, antiatherogenic and antiplasmodial activities. During structural definition of a FAD isolated from Croton pullei, the possibility of a heterologous series made this definition difficult. In this regard, computational simulations were performed using theoretical calculations at DFT level to predict Infrared (IR) and Nuclear Magnetic Resonance (NMR) data. The IR and NMR 13C and 1H data were compared with the theoretical calculations performed for three structural possibilities of a heterologous series. The theoretical results were compared with the experimental data through linear regression in order to define the most probable structure and showed satisfactory values.
Essential oil composition of Croton palanostigma Klotzsch from north Brazil
Brasil, Davi do Socorro B.;Muller, Adolfo Henrique;Guilhon, Giselle Maria S. P.;Alves, Cláudio Nahum;Andrade, Eloísa Helena A.;Silva, Joyce Kelly R. da;Maia, José G. S.;
Journal of the Brazilian Chemical Society , 2009, DOI: 10.1590/S0103-50532009000600026
Abstract: the essential oils of leaves, twigs, branches, trunk bark and fruits of croton palanostigma were analyzed by gc and gc-ms. the main compounds found in the oil of the leaves were linalool (25.4%), (e)-caryophyllene (21.0%), methyleugenol (17.2%) and β-elemene (6.0%); in the oil of the twigs were α-pinene (41.4%), limonene (29.0%), sabinene (11.5%) and β-pinene (5.7%); in the oil of the branches were methyleugenol (24.1%), (e)-methylisoeugenol (15.3%), α-pinene (11.2%) and (e)-caryophyllene (8.5%); in the oil of the trunk bark were a-pinene (31.6%), methyleugenol (25.6%) and (e)-methylisoeugenol (23.7%); and in the oil of the fruits were linalool (42.7%), methyleugenol (16.3%) and β-elemene (6.4%). statistical analysis showed that the leaves and fruit, and the branches and trunk bark, have significant similarities between them. in addition, the trunk bark oil has high brine shrimp larvicidal activity (lc50, 3.71 ± 0.01 mg ml-1).
Synthesis, X-ray crystal structure and theoretical calculations of antileishmanial neolignan analogues
Nascimento, Josenaide P. do;Santos, Lourivaldo S.;Santos, Regina Helena A.;Tozzo, érica;Ferreira, Janaina G.;Carmo, Maria Carolina L. do;Brasil, Davi S. B.;Alves, Cláudio N.;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010001000006
Abstract: the synthesis and x-ray crystal diffraction structure of two analogues of neolignans, 2-(4-chlorophenyl)-1-phenylethanone (20) and 2-[(4-chlorophenyl)thio]-1-(3,4-dimethoxyphenyl)propan-1-one (12) is described. the compound 12 presents activity against intracellular leishmania donovani and leishmania amazonensis amastigotes that cause cutaneous and visceral leishmaniasis. in addition, the density functional theory (dft) with the b3lyp hybrid functional was employed to calculate a set of molecular descriptors for nineteen synthetic analogues of neolignans with antileishmanial activities. afterwards, the stepwise discriminant analysis was performed to investigate possible relationship between the molecular descriptors and biological activities. through this analysis the compounds were classified into two groups active and inactive according to their degree of biological activities, and the more important properties were charges on some key atoms, electronic affinity and clogp.
Biotransformation of chalcones by the endophytic fungus Aspergillus flavus isolated from Paspalum maritimum trin
Corrêa, Marivaldo J. C;Nunes, Fátima M;Bitencourt, Heriberto R;Borges, Fábio C;Guilhon, Giselle M. S. P;Arruda, Mara S. P;Marinho, Andrey M. R;Santos, Alberdan S;Alves, Cláudio N;Brasil, Davi S. B;Santos, Lourivaldo S;
Journal of the Brazilian Chemical Society , 2011, DOI: 10.1590/S0103-50532011000700019
Abstract: the fungus aspergillus flavus isolated as endophytic of the plant paspalum maritimum trin. was evaluated for its potential application in biotransformation reactions. the compounds chalcone (1), 3,4,5-trimethoxychalcone (2) and 2,3,4,4'-tetramethoxychalcone (3) were biotransformed, respectively, in dihydrochalcone (4), 3,4,5-trimethoxydihydrochalcone (5) and 2,3,4,4'-tetramethoxydihydrochalcone (6). the structures were elucidated by spectroscopic methods including 1d and 2d nmr techniques, and ms analysis. the dihydrochalcones 5 and 6 are new compounds.
Método de calibra o de modelos de micro-simula o de tráfego através de otimiza o multivariada
Davi R. Campos Araújo,Gabriel B. Jacondino,Helena Beatriz B. Cybis,Carla S. ten Caten
Transportes , 2009,
Abstract: Este artigo apresenta um método para calibra o de simuladores microscópicos de tráfego, implementado através de projetos de experimentos com otimiza o multivariada. O estudo de caso foi desenvolvido em Porto Alegre, utilizando-se o modelo microscópico de simula o DRACULA. Nesse estudo, os parametros comportamentais do DRACULA s o calibrados para que o modelo reproduza os valores de indicadores de desempenho, como fluxos, tempos de viagem e comprimentos de fila, observados em campo. Os resultados obtidos foram satisfatórios e o método de calibra o aplicado apresentou-se eficiente.
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