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We investigated the effect of low temperature and urea combined with high pressure on tobacco mosaic virus (TMV). The evaluation of its aggregation state and denaturation process was studied using gel filtration, transmission electron microscopy, and spectroscopic methods. The incubation at 2.5 kbar induced 18% dissociation, and decreasing of temperature to -19 degreesC promoted additional dissociation to 72%, with stabilization of the dissociation products. Under such conditions, extensive denaturation did not occur. The apparent enthalpy and entropy of dissociation (Delta and TDelta) were -9.04 kcal/mol subunit and -15.1 kcal/mol subunit, respectively, indicating that the TMV association is an entropicly driven process. The apparent free energy of stabilization given by the presence of RNA is at least -1.7 kcal/mol subunit. Urea-induced dissociation of TMV samples and incubation at high-pressure promoted a higher degree of dissociation. The volume change of dissociation decreased in magnitude from -16.3 to -3.1 mL/mol of dissociated subunit, respectively, in the absence and presence of 2.5 M urea, suggesting exposure of the protein-protein interface to the solvent. High-pressure induced remarkable TMV denaturation in the presence of 2.5 M urea, with a volume change of -101 mL/mol of denatured subunit. The apparent enthalpy and entropy of denaturation (Delta and TDelta) by 1.75 M urea at 2.5 kbar was -11.1 and -10.2 kcal/mol subunit, respectively, demonstrating that the TMV protein coat presents an apparent free energy of denaturation by urea close to zero. Although the processes could not be assumed to be pure equilibria, these thermodynamic parameters could be derived by assuming a steady-state condition.

Recebido em 8/4/99 CURRICULAR DIRECTIONS FOR UNDERGRADUATE CHEMISTRY COURSES. 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. Keywords APRESENTAÇÃOAs discussões e diretrizes contidas neste texto foram elaboradas em atendimento à nova Lei de Diretrizes e Bases da Educação Nacional promulgada em 1996 (Lei 9.394/96) e do Edital n o 04/97 da Secretaria de Educação Superior do MEC, os quais estabelecem que os currículos dos cursos superiores precisam ser revistos, considerando o fim da exigência de currículo míni-mo e a necessidade de uma flexibilização curricular que, sem prejuízo de uma formação didática, científica e tecnológica só-lida, avance também na direção de uma formação humanística que dê condições ao egresso de exercer a profissão em defesa da vida, do ambiente e do bem estar dos cidadãos. INTRODUÇÃONo limiar deste novo século -e novo milênio -emerge uma nova subjetividade, um sentimento coletivo, generalizado, mundializado, traços de uma nova cultura em formação, de um novo momento histórico -a que muitos denominam pós-modernidade -caracterizado pela economia pós-industrial, pela compreensão do homem como um ser pluridimensional, pelo estabelecimento de novas concepções de limites, distâncias e tempo, pelo sentimento de responsabilidade em relação aos recursos naturais, pela busca de qualidade de vida. E repetindo, em outra dimensão, os movimentos de vanguarda do início do século XX, também agora, na base desta nova realidade, está a velocidade (não mais a mecânica, mas a eletrônica) com que têm sido gerados novos conhecimentos científicos e tecnológicos, rapidamente difundidos e absorvidos pelo setor produtivo e pela sociedade em geral.Como produtora de saber e formadora de intelectuais, docentes, técnicos e tecnólogos, a universidade contribui para a construção contínua do mundo e sua configuração presente. Por outro lado, sua amplitude e abrangência organizacional e possibilidade de ação resultam do modelo de país no qual se insere e das respectivas políticas educacionais. Assim, verificado este novo momento histórico, esta nova complexidade vivencial, veloz e mutante, a universidade brasileira precisa repensar-se, redefinir-se, instrumentalizar-se para lidar com um novo homem de um novo mundo, com múltiplas oportunidades e riscos ainda maiores. Precisa, também, ser instrumento de ação e construção desse novo modelo de país.A percepção desta nova realidade -hoje freqüentemente retratada pela mídia -evidencia-se pelas questões e discussões em curso no seio das próprias universidades, nas entidades ligadas à educação e nos setores de absorção do conhecimento e dos profissionais gerados pela universidade. É consenso entre professores, associações científicas e classistas, dirigentes de políticas educacionais e mesmo no geral da população instruí-d...

Background Among the many consequences of loss of CFTR protein function, a significant reduction of the secretion of bicarbonate (HCO 3 −) in cystic fibrosis (CF) is a major pathogenic feature. Loss of HCO 3 − leads to abnormally low pH and impaired mucus clearance in airways and other exocrine organs, which suggests that NaHCO 3 inhalation may be a low-cost, easily accessible therapy for CF. Objective To evaluate the safety, tolerability, and effects of inhaled aerosols of NaHCO 3 solutions (4.2% and 8.4%). Methods An experimental, prospective, open-label, pilot, clinical study was conducted with 12 CF volunteer participants over 18 years of age with bronchiectasis and pulmonary functions classified as mildly to severely depressed. Sputum rheology, pH, and microbiology were examined as well as spirometry, exercise performance, quality-of-life assessments, dyspnea, blood count, and venous blood gas levels. Results Sputum pH increased immediately after inhalation of NaHCO 3 at each clinical visit and was inversely correlated with rheology when all parameters were evaluated: [G′ (elasticity of the mucus) = − 0.241; G″ (viscosity of the mucus) = − 0.287; G* (viscoelasticity of the mucus) = − 0.275]. G* and G′ were slightly correlated with peak flow, forced expiratory volume in 1 s (FEV 1), and quality of life; G″ was correlated with quality of life; sputum pH was correlated with oxygen consumption (VO 2) and vitality score in quality of life. No changes were observed in blood count, venous blood gas, respiratory rate, heart rate, peripheral oxygen saturation of hemoglobin (SpO 2), body temperature, or incidence of dyspnea. No adverse events associated with the study were observed. Conclusion Nebulized NaHCO 3 inhalation appears to be a safe and well tolerated potential therapeutic agent in the management of CF. Nebulized NaHCO 3 inhalation temporarily elevates airway liquid pH and reduces sputum viscosity and viscoelasticity.

ABSTRACT:The spectroscopic behavior of Nile Red (NR) in solutions was investigated by spectrophotometric measurements and was calculated with the semiempirical intermediate neglect of differential overlap for spectroscopy (INDO/S) method. Two parametrizations implemented, respectively, by Pople and by Da Motta and Zerner, were employed; the solvent effects were simulated according to the dielectric continuum model [self-consistent reaction field (SCRF)], as well as with the explicit inclusion of solvent molecules. The calculations simulated reasonably well the experimental spectra and the intense solvatochromism of NR because the dipole moments were calculated to be higher in the first excited state than in the ground state. In addition, INDO/S calculations were carried out for partially optimized twisted conformers, whose electron donor moiety was orthogonal to the aromatic acceptor one and charge transfer was observed for excited states known as twisted intramolecular charge-transfer (TICT) states. In polar media, INDO/SϩSCRF calculations drastically stabilized the TICT state, reducing its energy down to the first excited state. Despite this intense solute-solvent stabilization, it is still less stable than the first excited state of the nontwisted, fully optimized conformer, and the limitations of the semi-empirical methods could not predict its role, if any, on the spectroscopic behavior of NR, except for the fact that the solvatochromism was explained independent of its presence.