Um potencial de interação para o estudo de materiais e simulações por dinâmica molecular

The Vashishta-Rahman effective interaction potential, based on the Pauling's concept of "ionic radii", has been successfully employed to investigate structural and dynamical properties of different classes of material. By celebrating Pauling's birth centenary, we review the building up of the Vashishta-Rahman potential and we present molecular-dynamics simulation results for structure and dynamics of superionic materials, chalcogenide glasses and metallic oxides.

Interação de compostos organossulfurados derivados do alho com o citocromo-c: um estudo eletroquímico

Organosulfur compounds present in garlic and onion have been evaluated as inhibitors of chemical carcinogenesis. Among them diallylsulfide was mainly investigated and studies demonstrated its metabolization to the corresponding sulfoxide and sulfone. In this work, we report the investigation of the interaction between the diallylsulfide and its oxidized derivatives, through cyclic voltammetry, with horse heart cytocrome-c (on a modified electrode with 4-mercaptopyridine). Our results suggest that there is a reversible interaction between cytocrome-c and diallylsulfide and diallylsulfone and an irreversible interaction with the diallylsulfoxide.

Intervalos de referência para elementos menores e traço em cabelo humano para a população da cidade do Rio de Janeiro - Brasil

Inductively coupled plasma mass spectrometry (ICP-MS) has been used for the determination of twenty minor and trace elements in hair samples from an urban population group (N = 1775), aiming at the establishment of reliable hair reference intervals. Statistical evaluation of the data with respect to age, sex and anatomic region was performed by multivariant analysis and according to recommendations of the International Federation of Clinical Chemistry (IFCC). The results show that mainly age and anatomic region (scalp or pubis) influence significantly the concentration of several elements. Comparison of the here calculated reference intervals with those previously published and used by clinical laboratories for this population showed larger discrepancies and the need for an urgent revision of these data.

Um novo modelo para os sítios de interação dos antagonistas H2, baseado na caracterização química dos sítios primário e secundário por QSAR- 3D

A new model for the H2 antagonists binding site is postulated based on adsorption coefficient values of sixteen antagonists, in the affinities constants of the primary and secondary binding sites, and in the chemical characterization of these sites by 3D-QSAR. All study compounds are in the extended conformation and deprotonated form. The lateral validation of the QSARs, CoMFA analysis, affinity constants and chemical similarity data suggest that the antagonists block the proton pump in the H2 receptor interacting with two tyrosines - one in the helix 5, and other in the helix 6.

Análise teórica da interação de CO, CO2 e NH3 com ZnO

This paper presents a study of the interaction of small molecules with ZnO surfaces by means of theoretical methods. The AM1 semi-empirical method was used for optimizing the geometric parameters of adsorbed molecules. The optimized AM1 structures were used in the calculations of the ab initio RHF method with the 3-21G* basis set. The interaction of CO, CO2 and NH3 molecules were studied with (ZnO)22 and (ZnO)60 cluster models. We have analyzed the interaction energy, SCF orbital energies, Mulliken charges and the density of states (DOS).

Validação do método de determinação simultânea dos íons brometo e bromato por cromatografia iônica em águas de consumo humano

European Directive (98/83/CE), compulsory after 2008, states that bromate in drinking water must be controlled at levels below 10 mg L-1. Supporting implementation of the Directive, the European Comission has established project SMT4-CT96 2134, in collaboration with various european institutions, aiming at the identification of the interferents to the current analytical method (Ionic Chromatography with Conductimetric Detection - IC/CD), their removal and the automation of pre-treatment and injection steps, as well as the development of alternative methods. EPAL, responsible for the water supply to a great deal of Portuguese regions, has taken steps to meet these requirements. Although not part of such project, this work (the result of a project conducted under a protocol of collaboration between EPAL SA and FCUL - Faculty of Sciences, University of Lisbon), reports on studies of usefulness to laboratories planning to monitor bromate in ozone treated waters, in conditions different from those described in EPA 300.1. Simultaneous determination of bromide is justified by its role as bromate precursor.

Análise de ácidos graxos não-esterificados de plasma humano por cromatografia gasosa capilar com injeção sem divisão de fluxo

The aim of the present work was to test the combination of non-esterified fatty acid (NEFA) isolation using fumed silicon dioxide with capillary gas-chromatography (C-GC) with splitless injection for the analysis of NEFAs in human plasma. Injection volume, solvent re-condensation and split purge flow-rate were the parameters evaluated for the analysis of fatty acid methyl esters by C-GC. The use of a solvent re-condensation technique, associated with 1.0 µL injection and a split purge flow rate of 80 mL/min resulted in satisfactory analysis of NEFAs. Fourteen fatty acids were identified in plasma samples, ranging from 2.03 to 184.0 µmol/L. The combination of both techniques proved useful for routine analyses of plasma NEFAs.

Management Estratégico. Su aplicación en la Gestión del Conocimiento y el Capital Humano

Es un libro en el que he tratado de destacar la cada día mayor vinculación existente entre las personas y el logro de la misión u objetivo supremo de la empresa. En la actualidad y en los próximos años, es imposible pensar que la empresa pueda alcanzar su misión sin una adecuada coordinación entre las personas y la estructura organizativa, teniendo en cuenta que el conocimiento es la base de todo ello lográndose a través de una determinada estrategia.

O ensino de química quântica e o computador na perspectiva de projetos

This paper aims to discuss and reflect about the use of computers in the teaching of Quantum Chemistry. A course on Computational Quantum Chemistry concentrating on Medicinal Chemistry projects was developed for undergraduate and graduate students. The results showed that students got more motivated and involved when there is an articulation between theory and practice. This work presents an alternative way to teach Theoretical Chemistry using projects.

O impacto industrial na composição química das águas subterrâneas com enfoque de consumo humano (Rio Grande, RS)

The alteration in the quality of groundwater in the industrial zone of Brazil's southernmost state was assessed by a hydrogeochemical study. In 70-85% of the studied area, fluoride, nitrate and phosphate in groundwater surpass the maximum limits for human consumption according to Brazilian environmental legislation. The chemical spectrum of contaminants and their spatial distribution show that fertilizer production processes are responsible for groundwater pollution. The natural conditions of the region are not favorable for minimal protection against infiltration of pollutants into the aquifer.

PARAFAC: uma ferramenta quimiométrica para tratamento de dados multidimensionais. Aplicações na determinação direta de fármacos em plasma humano por espectrofluorimetria

Since the last decade, the combined use of chemometrics and molecular spectroscopic techniques has become a new alternative for direct drug determination, without the need of physical separation. Among the new methodologies developed, the application of PARAFAC in the decomposition of spectrofluorimetric data should be highlighted. The first objective of this article is to describe the theoretical basis of PARAFAC. For this purpose, a discussion about the order of chemometric methods used in multivariate calibration and the development of multi-dimensional methods is presented first. The other objective of this article is to divulge for the Brazilian chemical community the potential of the combination PARAFAC/spectrofluorimetry for the determination of drugs in complex biological matrices. For this purpose, two applications aiming at determining, respectively, doxorrubicine and salicylate in human plasma are presented.

Contribuição à organização da pesquisa em Química e os desafios da interação com outras áreas do conhecimento

This article provides some aspects that allow making a current reading of the situation of the Brazilian Chemistry that permit us considerate it as a strategic area. They are still presented some initial proposals related to the organization of the research as well as to win the challenges of the relationship with the other areas of the knowledge.

Desenvolvimento de colunas cromatográficas de meios de acesso restrito proteína-imobilizada e suas avaliações para análise de fármacos com injeção direta de plasma humano

A series of bovine serum albumin-immobilized supports have been prepared and used as restricted access media (RAM) columns. Restricted-access supports combine size-exclusion of proteins and other high-molar-mass matrix components with the simultaneous enrichment of low-molar mass analytes. These characteristics were chromatographically evaluated for the columns. The RAM-BSA (Bovine Serum Albumin) columns showed excellent performance for exclusion of human plasma protein with good retention capacity for a series of acidic, basic, and neutral drugs.

Estudo teórico da interação existente entre a artemisinina e o heme

The purpose of this work is to study theoretically stereoelectronic aspects of the interaction between heme and artemisinin in the transitional heme-artemisinin complex. Through semi-empirical calculations using the PM3 method, the potential energy barrier of artemisinin rotation relative to heme in the heme-artemisinin complex was studied in vacuum and in the partially solvated state. The minimum heat of formation obtained for the complex with and without water molecules is -702.39 and -100.86 kcal mol-1, respectively, which corresponds to the dihedral angle C-Fe-O1-O2 of 43.93º and 51.90º around the iron-oxygen O1 bond, respectively. The water molecules bind to heme via 13 hydrogen bonds and O-H•••O and 6 C-H•••O interactions, which accounts for -67.23 kcal mol-1. It is observed that the inclusion of water molecules does not affect significantly the stability of the heme-artemisinin complex.

Espécies reativas de oxigênio e de nitrogênio, antioxidantes e marcadores de dano oxidativo em sangue humano: principais métodos analíticos para sua determinação

We review here the chemistry of reactive oxygen and nitrogen species, their biological sources and targets; particularly, biomolecules implicated in the redox balance of the human blood, and appraise the analytical methods available for their detection and quantification. Those biomolecules are represented by the enzymatic antioxidant defense machinery, whereas coadjutant reducing protection is provided by several low molecular weight molecules. Biomolecules can be injured by RONS yielding a large repertoire of oxidized products, some of which can be taken as biomarkers of oxidative damage. Their reliable determination is of utmost interest for their potentiality in diagnosis, prevention and treatment of maladies.