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Search Results: 1 - 10 of 289572 matches for " Hélio F.;Almeida "
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An investigation of the BSSE effect on the evaluation of Ab Initio interaction energies for cisplatin-water complexes
Lopes, Juliana Fedoce;Rocha, Willian R.;Santos, Hélio F. dos;Almeida, Wagner B. de;
Journal of the Brazilian Chemical Society , 2010, DOI: 10.1590/S0103-50532010000500017
Abstract: in this article the role played by the effective core potential (pt atom) on the evaluation of basis set superposition error (bsse) and interaction energies for the complex between cisplatin ([pt(nh3)2cl2]) and water was investigated. eight distinct spatial monomer orientations in the cisplatin-water complex were considered with the counterpoise procedure being employed to calculate the bsse. the bsse effect on potential energy curves, required for the determination of lennard-jones parameters, is also discussed. the calculations were performed at the hf, dft (blyp, b3lyp, bp86, pbe, pw91 functional) and mp2 level with pople's split valence and dunning's correlated consistent basis sets.
Structure and electronic properties of alkylthiophenes coupled by Head-to-Tail and Head-to-Head regioselectivity
Oliveira, Marcos A. de;Almeida, Wagner B. de;Santos, Hélio F. dos;
Journal of the Brazilian Chemical Society , 2004, DOI: 10.1590/S0103-50532004000600008
Abstract: in the present paper a theoretical analysis of alkylthiophenes with head-tail-head-tail (ht-ht) and head-head-tail-tail (hh-tt) regioselectivities up to 6 monomeric units was carried out. structure and electronic properties for the syn and anti forms were calculated by ab initio hartree-fock (hf) and density functional theory (dft) approaches. the energy gap between the conduction and valence bands was obtained at hf and dft levels and also calculated with the semiempirical zindo/s-ci method. the results showed that the isomer with hh-tt regioselectivity presents lower energy gap for longer oligomers and the substitution of thiophene by alkyl groups does not change significantly the energy gap. this is important in the sense that more processable polymers can be obtained through alkylation without decrease the energy gap that is a molecular properties related to the electronic conductivity. regarding to the conformational equilibrium, the syn form was found to be stable only for the ht-ht isomer and in this case the energy gap was found to be lower than those calculated for the anti form.
Reactivity of 5a,6-anhydrotetracycline platinum(II) complex with biological nucleophiles: a theoretical study
Marcial, Bruna L.;Costa, Luiz Ant?nio S.;De Almeida, Wagner B.;Dos Santos, Hélio F.;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000800002
Abstract: this paper describes a theoretical analysis of the interaction between 5a,6-anhydrotetracycline platinum(ii) complex (ahtc-pt) and some biological nucleophiles; adenine (a), guanine (g), cysteine (cys) and methionine (met). the aquated species [pt(ahtc)cl(h2o)]+ was taken as reagent for the processes studied here. for dna bases (a and g), the calculated values for δga,aq at the b3lyp/6-311+g(2d,p) level were 21.7 and 20.7 kcal mol-1 for interaction with a and g, respectively, which are in accordance with the expected behavior of faster process involving g. these values are higher than the experimental activation energy for the parent compound cisplatin (18.5 kcal mol-1 for interaction with g). for the process involving the amino-acids, the barriers were 17.6 (cys) and 18.5 kcal mol-1 (met), which are lower than the observed values for cisplatin (20.5 and 20.2 kcal mol-1, respectively). these outcomes show that ahtc-pt hybrid complex may be considered a promising lead compound in the development of novel anticancer drugs based on platinum complex.
Theoretical study of α-CD based [3] pseudorotaxanes: the role played by threadlike polymer on the stability of Cyclodextrin dimers
Anconi, Cleber P. A.;Nascimento Jr., Clebio S.;De Almeida, Wagner B.;Dos Santos, Hélio F.;
Journal of the Brazilian Chemical Society , 2008, DOI: 10.1590/S0103-50532008000500031
Abstract: cyclodextrins (cds) and polymeric chains have attracted considerable attention, being addressed in the literature as novel molecular assembly. the so-called "molecular necklace" synthesized by the inclusion of a polymeric chain inside cds cavity has been employed in the formulation of molecular wires and nanotubes. in this paper we applied our previous reported mixed basis set approach in order to investigate theoretically the α-cd inclusion complexes formed by two cd units and an oligo(ethylene glycol) (oeg). in attempt to analyze the role played by the oeg in the formation of pseudo-rotaxane in gas-phase, dft calculations were performed for six possible dimer associations of cds, named head-to-head (hh), tail-to-tail (tt) and head-to-tail (ht) with or without an oeg threadlike molecule included in the cavity formed by the α-cd dimer. the comparison between relative energies of empty (hh, tt and ht) and filled associations (hh-oeg, tt-oeg and ht-oeg) shows that the oeg chain does not interfere significantly in the relative stabilization energies of the supramolecular systems, therefore the relative arrangements of cds in the necklace structures should be primarily driven by interactions between cyclodextrin units.
Espectro infravermelho e análise conformacional do composto 3-fenil-2-oxo-1,2,3-oxatiazolidina
Santos, Hélio F. dos;Almeida, Wagner B. de;Val, Amélia M. G. do;Guimar?es, Afonso C.;
Química Nova , 1999, DOI: 10.1590/S0100-40421999000500017
Abstract: the infrared (ir) spectra of the four distict conformers located on the multidimensional potential energy surface (pes) for the 3-phenyl-1,2,3-oxathiazolidine 2-oxide compound have been calculated using the semiempirical quantum-mechanical method pm3. the band spectra are reported and compared directly with the experimental spectrum. the ir intensities are shown to be much more sensitive to conformational changes than the vibrational frequencies and so, the theoretical analysis of the ir spectrum can be used as a tool for helping in the elucidation of the structure of heterocyclic compounds.
Espectro infravermelho e análise conformacional do composto 3-fenil-2-oxo-1,2,3-oxatiazolidina
Santos Hélio F. dos,Almeida Wagner B. de,Val Amélia M. G. do,Guimar?es Afonso C.
Química Nova , 1999,
Abstract: The infrared (IR) spectra of the four distict conformers located on the multidimensional potential energy surface (PES) for the 3-phenyl-1,2,3-oxathiazolidine 2-oxide compound have been calculated using the semiempirical quantum-mechanical method PM3. The band spectra are reported and compared directly with the experimental spectrum. The IR intensities are shown to be much more sensitive to conformational changes than the vibrational frequencies and so, the theoretical analysis of the IR spectrum can be used as a tool for helping in the elucidation of the structure of heterocyclic compounds.
Desenvolvimento Sustentável: análise das rela??es interorganizacionais na indústria de celulose e papel
Oliva, Fábio Lotti;Sobral, Maria Cecília;Teixeira, Hélio Janny;Grisi, Celso Cláudio de Hildebrand e;Almeida, Martinho Isnard Ribeiro de;
Ambiente & Sociedade , 2012, DOI: 10.1590/S1414-753X2012000100006
Abstract: the paper presents the outcomes of the application of a model of systematization of the process of analysis of the relations of influences between public and private agents geared towards sustainable development in the alto tietê region, within the s?o paulo macro-metropolis, specifically within the paper and cellulose industry. for this purpose a theoretical framework was developed adjusted to the conflictive dynamics between economic, social and environmental interests. the theoretical support was reached through the composition of several conceptual approaches: theory of open systems, new institutional economy and networked organizations. research action was the method followed to deepen the study of the relations of those agents involved in the cellulose and paper industry in the municipality of suzano. the illustration of the model′s application, with the data obtained, serves to show an analytical perspective for the study of the relations between those agents involved in economic activities, taking into account sustainable development.
Leishmaniose tegumentar americana em centro de treinamento militar localizado na Zona da Mata de Pernambuco, Brasil
Brand?o-Filho, Sinval P.;Brito, Maria E. Felinto de;Martins, Clediane A. Pereira;Sommer, Iara B.;Valen?a, Hélio F.;Almeida, Francisco A.;Gomes, Judilson;
Revista da Sociedade Brasileira de Medicina Tropical , 1998, DOI: 10.1590/S0037-86821998000600012
Abstract: an outbreak of american cutaneous leishmaniasis has been occurred in military training unit localized in 'zona da mata' of pernambuco state, brazil, where were registered 26 human cases. an epidemiological survey was carried out by entomological investigation and montenegro skin test (mst). lutzomyia choti presents predominance (89.9%) in sandflies identified. out of 545 men who realized training activities were 24.12% positive to mst.
A utiliza??o da artéria torácica interna aumenta a mortalidade hospitalar do paciente coronariano idoso revascularizado?
Iglézias, José Carlos R;Dallan, Luís Alberto;Louren?o Filho, Domingos D;Fabri, Hélio Ant?nio;Ramires, Ant?nio F;Luz, Protásio Lemos da;Oliveira, Sérgio Almeida de;Pileggi, Fúlvio;Jatene, Adib D;
Revista Brasileira de Cirurgia Cardiovascular , 1991, DOI: 10.1590/S0102-76381991000200008
Abstract: at the heart institute, we performed a study to evaluate if the internal thoracic artery modified the nosocomial mortality of elderly coronary patients (age 70 years), submitted to elective isolated revascularization of the myocardium. clinical, hemodynamic, radiologic, operative and postoperative parameters were included in the protocol. in a prospective study one hundred consecutive patients, with complete observations were analysed. the statistical analysis was performed using pearson's x 2 test. the results of this study showed that there was a statistically significant difference between the groups, the nosocomial mortality being higher in that in which autogenous saphenous vein grafts were used. the role of the surgeon as a screener regarding obtention of results is also discussed.
Isolation and amino acid sequencing by MALDI-TOF-MS/MS of a novel antimicrobial anionic peptide from the skin secretion of Osteocephalus taurinus (Anura, Hylidae)
Costa,lio O. G.;Almeida, Richardson A.;Melo, Jorge T.;Koolen, Hector H. F.;Silva, Felipe M. A. da;Leite, José Roberto S. A.;Prates, Maura V.;Bloch Jr., Carlos;Pinto, Angelo C.;
Journal of the Brazilian Chemical Society , 2012, DOI: 10.1590/S0103-50532012001200002
Abstract: by means of chromatographic techniques, a novel anionic peptide, named otacidin, was isolated from the skin secretions of tree brazilian anurans osteocephalus taurinus. the de novo sequencing of the amino acids was performed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (maldi-tof-ms/ms) analyses. the antimicrobial potential of this novel metabolite was evaluated against escherichia coli and pseudomonas aeruginosa, being observed minimum inhibitory concentration (mics) of 37.4 and 78.4 mm, respectively. this work is just the second report of an antimicrobial anionic peptide from an amphibian.
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