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Search Results: 1 - 10 of 362640 matches for " Cleydson B. R. dos Santos "
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Computational Analysis of Physicochemical, Pharmacokinetic and Toxicological Properties of Deoxyhypusine Synthase Inhibitors with Antimalarial Activity  [PDF]
Nayara S. R. Silva, Luana K. S. Gon?alves, Jonatas L. Duarte, Juliane S. Silva, César F. Santos, Francinaldo S. Braga, Raí C. Silva, Josivan S. Costa, Lorane I. S. Hage-Melim, Cleydson B. R. dos Santos
Computational Molecular Bioscience (CMB) , 2014, DOI: 10.4236/cmb.2014.44006
Abstract: Malaria is a parasitic disease which has as etiological agents protozoa of the genus Plasmodium prevalent in tropical countries. The appearance of Plasmodium strains resistant to artemisinin has become necessary the development of new drugs using computational tools to combat this epidemic. Diverse transporter proteins can act as antimalarials targets, thereby being the enzyme deoxyhypusine synthase a promising antimalarial target. The present study aimed to investigate 15 most active inhibitors of deoxyhypusine synthase target, deposited in databases Binding DB, in order to trace a pattern of physicochemical, pharmacokinetic and toxicological properties of the inhibitors for this enzyme and propose new inhibitors of deoxyhypusine synthase target. The physicochemical properties were obtained according to the Lipinski parameters to evaluate oral absorption. Based on the certain properties were proposed three new inhibitors (A, B and C). The ADME/Tox properties were calculated for new inhibitors compared with results of the selected compounds. The fifteen inhibitors for oral administration showed satisfactory results, because they have adapted to the Lipinski parameters. In relation to the penetration of the blood-brain barrier the inhibitors analyzed showed penetration values less than 1, and ranged from 0.0411815 to 0.481764, being that the compound 1 showed value of CBrain/CBlood = 0.135467. Compound B showed a higher strength in plasma protein binding in relation to the compound 1, having a variation be-tween them of ±1.489344. Therefore, the compound B would present a longer halflife compared with compound 1. The proposed compounds showed positive and satisfactory results, being able to reach less adverse effects related to the central nervous system depending of administered dose.
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.
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.
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.
Study of Calcium and Sodium Behavior to Identify Milk Adulteration Using Flame Atomic Absorption Spectrometry  [PDF]
Poliana M. dos Santos, Lenon F. B. Costa, Edenir R. Pereira-Filho
Food and Nutrition Sciences (FNS) , 2012, DOI: 10.4236/fns.2012.39161
Abstract: A fast and direct method for determination of milk adulteration by monitoring of calcium and sodium concentrations variations was described. Milk samples were furnished by a dairy company located at S?o Carlos (S?o Paulo State, Brazil) and and spiked with tap-water, whey, hydrogen peroxide, synthetic urine, urea and synthetic milk in the ranged from 5% to 50% (v/v), expect for caustic soda. Caustic soda was added in the milk until establish the original pH. The milk samples were analyzed by using flame atomic absorption spectrometry (FAAS) and no acid digestion process was required. Results showed a significant decrease in the Na and Ca concentrations with addition of synthetic milk and tap-water, a nonlinear variation with addition of synthetic urine, whey and hydrogen peroxide and a largest increase in the Na concentration with addition of NaOH. Correlation between Na and Ca concentrations in pure and adulterated milk were evaluated by paired t-test at a 95% confidence level. Results showed that the method proposed is efficient to identify samples adulterated with tap-water, caustic soda, synthetics milk and urine.
Actual Evapotranspiration Estimation Using Remote Sensing: Comparison of SEBAL and SSEB Approaches  [PDF]
Bergson G. Bezerra, Bernardo B. da Silva, Carlos A. C. dos Santos, José R. C. Bezerra
Advances in Remote Sensing (ARS) , 2015, DOI: 10.4236/ars.2015.43019
Abstract: The main objective of this paper was to evaluate the daily actual evapotranspiration (ET) accuracy obtained by remote sensing algorithms when compared with Bowen ratio measurements performed in the cotton fields. The experiment was conducted in a cotton experimental field of EMBRAPA located in Ceará State, Brazil. Seven TM Landsat-5 images acquired in 2005 and 2008 were used to perform SEBAL and SSEB algorithms. The comparison between the estimated values by remoting sensing algorithms and the measured values in situ showed an acceptable accuracy. Besides, SSEB algorithm showed to be an important tool for ET analysis in the semi-arid regions, due to the fact that it does not need the meteorological data to solve the energy balance, but only the average temperature of the “hot” and “cold” pixels. Additionally, SSEB presents simpler processing than SEBAL algorithm that needs to solve an iterative process to obtain the sensible heat flux values.
Impacto de altera??es ambientais na ecologia de flebotomíneos no sul do Brasil
Teodoro, Ueslei;Kühl, Jo?o B.;Santos, Demilson R. dos;Santos, élcio S. dos;
Cadernos de Saúde Pública , 1999, DOI: 10.1590/S0102-311X1999000400025
Abstract: tree felling around a chicken coop and periodic insecticide spraying at the palmital farm in the county of terra boa in southern brazil impacted the ecology of sand fly species. the most prevalent species (51.6%) before clearing the trees and insecticide spraying was lutzomyia migonei (fran?a, 1920), and it is now lutzomyia (nyssomyia) whitmani (antunes & coutinho, 1939) (89.8%). there was a highly significant difference between the proportions of l. whitmani reported by this paper (89.8%) and another publication before the tree felling and insecticide spraying (32.6%).
Impacto de altera es ambientais na ecologia de flebotomíneos no sul do Brasil
Teodoro Ueslei,Kühl Jo?o B.,Santos Demilson R. dos,Santos élcio S. dos
Cadernos de Saúde Pública , 1999,
Abstract: Verificou-se que a abertura de uma clareira ao redor de um galinheiro e aplica es periódicas de inseticidas refletiram na ecologia das espécies de flebotomíneos na Fazenda Palmital, município de Terra Boa, Estado do Paraná, sul do Brasil. A espécie dominante (51,6%) antes do desmatamento e das aplica es de inseticidas era Lutzomyia migonei (Fran a, 1920). Após estas medidas, Lutzomyia (Nyssomyia) whitmani (Antunes & Coutinho, 1939) passou a predominar (89,8%). A diferen a de propor es de L. whitmani nesta investiga o (89,8 %) em rela o à outra (32,6%), realizada antes da abertura da clareira e das aplica es de inseticidas, foi altamente significativa.
Consumo quantitativo e qualitativo de Perifíton colonizado em substrato artificial Biomphalaria Tenagophila (Gastropoda, Planorbidae)
Santos, M. B. L. dos;Freitas, J. R. de;
Memórias do Instituto Oswaldo Cruz , 1986, DOI: 10.1590/S0074-02761986000400002
Abstract: snails reared in the field in transparent and darkened cages consumed similar daily quantities of periphyton, although the former comprised more plant and the latter more animal material. the daily consumption per snail increased significantly in the presence of greater quantities of food, but the proportion consumed of the total food available decreased.
Effect of Nb2O5·nH2O Termal Treatment on the Esterification of a Fatty Acid  [PDF]
Deborah A. dos Santos, Valdemar Lacerda Jr., Júlia Trist?o do C. Rocha, Reginaldo B. dos Santos, Sandro J. Greco, Alvaro C. Neto, Renzo C. Silva, Eustáquio V. R. de Castro
Modern Research in Catalysis (MRC) , 2013, DOI: 10.4236/mrc.2013.23010
Abstract:

In general, esterification reactions are favored by the increase in reaction temperature, excess of one of the reactants (usually alcohol), and additions of acid or basis catalysts. Esterification of oleic acid with methanol catalyzed by Nb2O5·nH2O calcined at different temperatures showed good conversion rates, especially at reaction temperature of 100°C and higher catalyst proportions. PLS calibration showed good results for predicting the amounts of methyl oleate in reaction products.

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