Biocatálise em meios aquo-restritos: fundamentos e aplicações em química analítica

The ability of enzymes to function in aquo-restricted media (commonly reported as non-aqueous media) has greatly enlarged the applications in numerous fields. The development of biosensors was also benefited with this area, expanding their applications toward many previously inaccessible analytes, enlarging significantly the scope of applications. In this review, some basic factors that influence biocatalytical reactions in aquo-restricted media is discussed. Attention is focused on the development, advantages and analytical applications of biosensors in non-aqueous media. Recent examples and relevant applications of their use are presented.

A pesquisa como perspectiva de formação continuada do professor de química

The education of a chemistry teacher is not being seen as a specific preparation for the exercise of a professional activity, which differs from the professional activity of a chemist or a chemistry researcher. This happens because in the academic field, mainly in the exact and natural sciences, the idea that knowing a determined subject is enough to be able to teach it, is tacitly accepted. This is, actually, the first condition to be able to be a university professor. There is another necessary condition for competent teaching: to have specific professional knowledege of teaching. I defend that this knowledge can be constitued in the interaction with other professionals in the form of research. Thus, as a chemist constitutes himself through the research in the interaction with other chemists, the teacher develops himself in this professional field in the interaction with other teachers and the permanent attitude of researching.

Prêmio Nobel de Química em 1998: Walter Kohn e John A. Pople

A résumé of the evolution of quantum chemistry methodologies is presented. The pioneering contributions of John A. Pople and Water Kohn, the 1998 Nobel Prize Laureates in Chemistry, to the development of quantum chemistry computational methods for studying the properties of molecules and their interaction is discussed.

Algoritmo genético em química

Genetic algorithm is an optimization technique based on Darwin evolution theory. In last years its application in chemistry is increasing significantly due the special characteristics for optimization of complex systems. The basic principles and some further modifications implemented to improve its performance are presented, as well as a historical development. A numerical example of a function optimization is also shown to demonstrate how the algorithm works in an optimization process. Finally several chemistry applications realized until now is commented to serve as parameter to future applications in this field.

La formación de habilidades en Química General en la perspectiva de la teoría de P. Ya. Galperin, como actividad de contrucción de conocimientos

Thir paper presents the results of a pedagogical experiment conducted with chemistry students of the mechanical engineering curriculum. The aim of the experiment was to study the development of the a general ability for the study program as a process of knowledge construction based on the theory of assimilation of P. Ya. Galperin.

Avaliação dos programas de pós-graduação em química no Brasil

A broad picture of the graduate programs in chemistry in Brazil is analyzed from the data collected during the period 1996/1997 for evaluation by CAPES. The results are compared with those from previous evaluations, indicating significant quantitative and qualitative progresses.

Diretrizes curriculares para os cursos de química

As a result of a number of discussions on the quality of undergraduate courses in Brazilian universities, curricular directions have been proposed. We present herein the curricular directions for the Chemistry courses with respect to basic, professional and complementary contents and extra-class activities.

Química orgânica experimental: integração de teoria, experimento e análise

A new approach for teaching in basic experimental organic chemistry is presented. Experimental work goes on parallel to theoretical lectures leading to an immediate application of theoretical concepts transmitted therein. One day/week is dedicated exclusively to the organic laboratory. Reactions are proposed as problems to be solved; the student has to deduce the structure of the product on the basis of his observations, the analytical data and his mechanistical knowledge. 70 different experiments, divided in 7 thematical chapters, are presented. All experiments require the analysis and discussion of 1H and 13C NMR, IR and UV spectra. Additional questions about each reaction have to be answered by the student in his written report. Laboratory safety is garanteed by the exclusion or substitution of hazardous and toxic reagents. Microscale preparations are adopted in most cases to lower the cost of materials and the amount of waste. Recycling of many reaction products as starting materials in other experiments reduces the need for commercial reagents and allows the execution of longer reaction sequences. Only unexpensive standard laboratory equipment and simple glassware are required. All experiments include instructions for the save treatment or disposal of chemical waste.

Avaliando as aproximações usadas no ensino de Físico-Química

The approaches are part of the everyday of the Physical Chemistry. In many didactic books in the area of Chemistry, the approaches are validated starting from qualitative and not quantitative approaches. We elaborated some examples that allow evaluating the quantitative impact of the approaches, being considered the mistake tolerated for the approximate calculation. The estimate of the error in the approaches should serve as guide to establish the validity of the calculation, which use them. Thus, the shortcut that represents a calculation approached to substitute accurate calculations; it can be used without it loses of quality in the results, besides indicating, as they are valid the adopted criterions.

A influência da Química nos saberes médicos acadêmicos e práticos do século XVIII em Portugal e no Brasil

At the dawn of the eighteenth century chemistry was establishing itself as a physical science on its own right, after a long ancillary relationship with medicine and pharmacy, which had began two centuries before. This association, and the many changes that came along the scientific revolution spread into many walks of life. The Luso-Brazilian world, apparently so removed from the new developments, could not help to be touched by them, as this study shows, in which two contemporary medical authors are analysed. Both were Portuguese who had long lived in Brazil; both practised and wrote extensively on Medicine; both felt the influence of the new times, albeit in quite different ways.

Composição química da glândula abdominal da fêmea da mariposa Castnia licus (Drury) (Lepidoptera:Castniidae): possíveis feromônios e precursores

The hexane and methanolic extracts from pheromonal glands of Castnia licus (Drury) virgin females have been studied. Analyses by gas chromatography and mass spectrometry allowed us to determine the major constituents present in the hexane extract as n-alkanes C21 to C30, (Z)-9-hexadecenoic acid (C16), and (Z)-9-octadecenoic acid (C18) and hexadecanoic acid (C16). Aldehyds, alkenes and acetates were also detected in low concentrations in the extracts. Female pheromone glands were analysed for pheromone precursors using the methanolic extract. In addition to the compounds methyl hexadecanoate and methyl (Z)-9-octadecenoate, the glandular tissue contains a homologous series of methyl esters from C12 to C24. The hexane extract of the female abdomenal glands elicited activity from males in a behavioural bioassay.

Elementos da dinâmica química ao nível da teoria variacional do estado de transição com correções interpoladas

In this article are presented some fundamental elements of the conventional and of the variational transition state theories which are needed to carried out calculations of semi-classical chemical dynamics. Some important bottlenecks in building reliable potential energy surfaces using electronic structure calculations are also discussed. It is put emphasis on the methodology of the variational transition state theory with interpolated corrections (VTST-IC), and its application in the calculations of the rate constants and of the kinetic isotope effect (KIE) of CH4 + Cl « CH3 + HCl reaction.

Processo químico industrial de extração de óleo vegetal: um experimento de química geral

In this study we describe an experimental procedure based on a chemical industrial process of soya-bean oil extraction applied in general chemistry for undergraduate students. The experiment was planned according to the Science, Technology and Society (STS) approach to teach basic chemical concepts and provide grounding in the management of environmental care. The use of real life chemistry problems seems to salient the relevance of chemistry to our students and enhances their motivation to learn both the practical and theoretical components of the discipline.

Alguns aspectos de imunoensaios aplicados à química analítica

In the last years, the use of antibody-antigen interactions, has earned attention not only for clinical analysis, but also for food industry and environmental control. Since the scope and diversity of immunoassay technology have shown a wide development. Continuous advances in order to analyse complex matrices, to improve reliability, simplicity (nonseparation) and to get multiple simultaneous assays, and extreme sensitivity (lower than zeptomole detection limits) are increasing. Many strategies have been investigated including chemiluminescent enzyme immunoassays, DNA as label and development of flow injection and immunosensors techniques. This subject became very usefull and important in nowadays that are taught in the undergraduate courses of chemistry in the european universities. However in our country are still ignored in the chemistry course.

Construção de modelos para ilustração de estruturas moleculares em aulas de química

This paper describes the construction of a kit of molecular model for illustration of molecular structure in chemical class using cheap materials. The atoms were represented by plastic spheres and the bonds between the atoms were made from plastic straws which were cut in the required length using a scale of 1.6 cm corresponding to 100 pm. Examples of adaptations made in this kit for didactical application are given.