Editorial O biodiesel e a política de C & T brasileira Suarez, Paulo A. Z. Meneghetti, Simoni M. P. Ferreira, Vitor F. |
Artigo Determination of lamivudine, stavudine and nevirapine in tablets by high performance liquid chromatography Silva, Gisele Rodrigues da Lages, Gustavo Portela Pianetti, Gerson Antônio Nunan, Elzíria de Aguiar Soares, Cristina Duarte Vianna Campos, Ligia Maria Moreira de Abstract in English: A high performance liquid chromatography method was developed to quantify lamivudine, stavudine and nevirapine combined in tablets. The separation was carried out in less than 10 min using a phosphate buffer of pH 3.0 and acetonitrile (75:25, v/v) as mobile phase, a LiChrospher ODS column and UV detection at 266 nm. The method was linear over the range of 15-135 µg/mL (lamivudine), 4-36 µg/mL (stavudine) and 20-180 µg/mL (nevirapine). The accuracy ranged from 98.56 to 102.04% and intra-day and inter-day precision was less than 1% for the three drugs. The method showed robustness, remaining unaffected by deliberate variations in relevant parameters. |
Artigo HPLC analysis of nicotinic acid, trigonelline, chlorogenic acid and caffeine in roasted coffee Alves, Sandriel Trindade Dias, Rafael Carlos Eloy Benassi, Marta de Toledo Scholz, Maria Brígida dos Santos Abstract in English: A reverse phase liquid chromatography method was developed for simultaneous determination of trigonelline, caffeine, nicotinic and chlorogenic (5-CQA) acids in roasted coffee. A gradient of acetic acid/acetonitrile was used as mobile phase and detection was carried out in the UV. The samples were extracted with acetonitrile/water (5:95 v/v) at 80 ºC/10 min. Good recovery (89 to 104%), repeatability and linearity were obtained. Detection limits of 0.01, 0.15, 0.04 and 0.04 mg mL-1 were observed for nicotinic acid, trigonelline, 5-CQA and caffeine. The method, applied to arabica and robusta coffees with different degrees of roasting, was efficient and fast (~35 min) and also allowed identification of cinnamic acids. |
Artigo A novel approach to quantify organic mercury (organic Hg) by cold vapour atomic fluorescence spectroscopy (CVAFS) Bisinoti, Márcia Cristina Jardim, Wilson F. Brito Júnior, José Lailson Malm, Olaf Guimarães, Jean Remy Abstract in English: In this work a simple and sensitive procedure to extract organic mercury from water and sediment samples, using methylene chloride in acidic media followed by CVAFS quantification has been developed. The method was evaluated for possible interferents, using different inorganic mercury species and humic acid, no effects being observed. The detection limit for organic mercury was 160 pg and 396 pg for water and sediment samples respectively. The accuracy of the method was evaluated using a certified reference material of methylmercury (BCR-580, estuarine sediment). Recovery tests using methylmercury as surrogate spiked with 1.0 up to 30.0 ng L-1 ranged from 90 up to 109% for water samples, whereas for sediments, recoveries ranged from 57 up to 97%. |
Artigo Comparative study of silica obtained from acid leaching of rice husk and the silica obtained by thermal treatment of rice husk ash Della, Viviana Possamai Hotza, Dachamir Junkes, Janaína Accordi Oliveira, Antonio Pedro Novaes de Abstract in English: A comparison between silica by acid leaching of rice husk (RH) and silica obtained from thermal treatment of rice husk ash (RHA) is presented. The best leaching results were obtained using 10% hydrochloric acid followed by washing with water. The alternative method, calcination of RHA at 700 ºC for 6 h followed by grinding for 80 min, was more effective. Silica obtained from RH was about 97% amorphous, had a 17.37 µm mean particle size, and a specific surface area of 296 m²/g. On the other hand, for silica obtained from RHA the values were about 95% amorphous material 0.68 µm, and 81 m²/g. |
Artigo Styrene polymerization using organolanthanide compounds activated by MAO Maia, Alessandra de Souza Quini, Josué Garcia Miotti, Renata Diana Oliveira, Wanda de Abstract in English: In an attempt to improve the performance of organolanthanide catalysts we investigated the use of the industrially important cocatalyst methylaluminoxane (MAO) to activate organolanthanide compounds in olefin polymerization. The catalytic systems LnBrCp2(THF)2/MAO (Cp=cyclopentadienyl) and LnBrCp*2THF/MAO (Cp*= pentamethylcyclopentadienyl), Ln=Pr and Yb, were active in styrene polymerization but inactive in ethylene and propylene polymerization. These systems produced atactic polystyrene with conversions of up to 8.2% (PrBrCp*2THF, Al/Ln=200, T=80ºC, t=4 h) in toluene. In the absence of solvent, the conversion is 26.0% (1.5 h) and the molar mass of the atactic polystyrene is almost ten times higher (43 kg/mol). |
Artigo Phenolic constituents and terpenoids isolated from the roots of Andira fraxinifolia (Fabaceae) Silva, Virginia Claudia da Alves, Aline Nogueira Santana, Alessandra de Carvalho, Mário Geraldo de Silva, Sandra Lúcia da Cunha e Schripsema, Jan Abstract in English: Sitosterol, stigmasterol, betulinic acid, lupeol, 3-O-beta-D-glucopiranosylsitosterol, 3-O-alpha-L-rhamnopiranosylchromone, 5,7-dihydroxy-4'-methoxyisoflavone, 3',5,7-trihydroxy-4'-methoxyisoflavone and a mixture of two rel-2R,3S-3-O-alpha-L-rhamnopiranosilflavanonols were isolated from the roots of Andira fraxinifolia. Their structures were established by spectral data analysis. |
Artigo Effects of the substituents on the hydrogen bond of 3-hydroxypropenal Rustici, Valéria C. F. Caramori, Giovanni F. Galembeck, Sérgio E. Abstract in English: The effect of substituents on the energies and geometries of 3-hydroxypropenal was studied using the B3LYP/6-311++G(d,p) model. The hydrogen bond energies indicate that the strongest donors and the weakest acceptors present the highest and the weakest hydrogen bonds, respectively, indicating the validity of the Madsen RAHB model. Geometric parameters indicate that the intensity of the hydrogen bond is proportional to the resonance, as suggested by the RHAB model. The effect of substituents diverges from the model proposed by Gilli et al. Sometimes the results indicate that the donor or acceptor effect is more important than the point of substitution. |
Artigo Determination of contaminants in used lubricating oils and in wastewater contamined by these lubricants Silveira, Eva Lúcia Cardoso Caland, Lília Basílio de Moura, Carla Verônica Rodarte de Moura, Edmilson Miranda Abstract in English: A simple and reliable ashing procedure is proposed for the preparation of used lubricating oil samples for the determination of Zn, Fe, Pb, Ni and Cu by the flame atomic absorption spectrometry technique. Sulphanilic acid was added to oil samples, the mixture coked and the coke ashed at 550 ºC. The solutions of the ash were analysed by flame AAS for these metals. The quantification limits were 38.250 µg g-1 for Zn, 4.550 µg g-1 for Fe, 1.562 µg g-1 for Pb, 1.450 µg g-1 for Ni, and 0.439 µg g-1 for Cu. The determinations, in lubricating oil, showed good precision and accuracy with recoveries between 90 and 110 %, indicating a negligible matrix effect in the experiments using addition of analyte, with relative standard deviation lower than 5%. The results for analysis of wastewater contamined by theses lubricants showed a very high relative standard deviation. |
Artigo Chemical characterization of Ocimum basilicum L. extracts obtained by high pressure CO2 extraction Mazutti, Marcio Beledelli, Bernardo Mossi, Altemir José Cansian, Rogério Luís Dariva, Cláudio Oliveira, José Vladimir de Paroul, Natália Abstract in English: This work reports extraction yield and chemical characterization of the extracts obtained by high-pressure CO2 extraction of a cultivar of Ocimum basilicum L. The experiments were performed in the temperature range of 20 to 50 °C, from 100 to 250 atm of pressure. Chemical analyses were carried out by gas chromatography coupled to mass spectrometry, permitting to identify 23 compounds that were grouped into five chemical classes. Results showed that temperature and solvent density influenced positively the extraction yield. At 20 °C and 0.41 g cm-3 occurred a rise in the concentration of monoterpenes, oxygenated monoterpenes, sesquiterpenes and oxygenated sesquiterpenes. |
Artigo Chemical variation in the essential oil of Hyptis suaveolens (L.) Poit., under cultivation condition Martins, Felipe Terra Santos, Marcelo Henrique dos Polo, Marcelo Barbosa, Luiz Cláudio de Almeida Abstract in English: This study was performed to establish the correlation between the growth conditions and essential oil composition of Hyptis suaveolens from Alfenas (MG), Brazil. The plants were grown in a greenhouse, four treatments were used and they were harvested at two different periods of time (60 and 135-day-old plants). The essential oil composition was determined by GC-MS analysis. The terpenes spathulenol, globulol, dehydroabietol, a-cadinol and beta-phellandrene were the major constituents found in the essential oil. Oxygenated sesquiterpenes represented the main group of constituents in most of the treatments. The major changes in the essential oil composition were found in 135-day-old plants grown under NPK deficiency. We also identified three groups of volatile components that have not been previously described in H suaveolens. |
Artigo Focused-microwave-assisted digestion of encapsulated lubricating oils: gradual sample addition to pre-heated acid Bressani, Flavia A. Silva, Hamilton O. Nóbrega, Joaquim A. Costa, Letícia M. Nogueira, Ana Rita A. Abstract in English: The applicability of the recently proposed procedure based on gradual sample addition to microwave-assisted pre-heated concentrated acid is limited by the sample viscosity. In this work, lubricating oil samples with high viscosity were encapsulated and manually added to the microwave-assisted pre-heated concentrated digestion mixture. The procedure was applied for determination of Al, Ca, Cr, Cu, Fe, Mg, Ni, P, Pb, Si, Sn, Sr, V, W, and Zn in lubricating oil by inductively coupled plasma optical emission spectrometry (ICP OES). Determined and certified values for Ca, Mg, P, and Zn in lubricating oil were in agreement at a 95% confidence level. |
Artigo Structural aspects related to the ion exchange process in layered niobate K4Nb6O17 Bizeto, Marcos A. Christino, Fernando P. Tavares, Marina F. M. Constantino, Vera R. L. Abstract in English: The niobate with formula K4Nb6O17 has a layered structure formed by stacked negative sheets and exchangeable cations in the interlayer region. In this study we discuss some structural aspects related to the ion exchange in layered hexaniobate based on X-ray diffractometry and vibrational Raman spectroscopy data. Hexaniobate has two distinct interlayer regions and the potassium ions of one interlayer in particular are preferably exchanged by other cations, leading to an interstratified material. |
Artigo Effect of drying air temperature upon the content and chemical composition of the essential oil from Lippia alba (Mill) N. E. Brown Barbosa, Fabrizio da F. Barbosa, Luiz C. A. Melo, Evandro C. Botelho, Fernando Mendes Santos, Ricardo H. S. Abstract in English: Leaves of Lippia alba were submitted to six different drying treatments, using air at ambient temperature and heated up to 80 °C. The essential oil was extracted by steam distillation and analyzed by GC-MS. For the dried leaves, the oil content was reduced by 12 to 17% when compared with the fresh plant (0.66%). The major oil component was citral, representing 76% for the fresh plant, and varying from 82 to 84% for the dried material. These results showed that L. alba can be submitted to a drying process of up to 80 ºC without degradation and/or loss of the major, [LC1] active component. |
Artigo Phenol adsorption on commercial active carbon under alkaline conditions Guilarduci, Viviane Vasques da Silva Mesquita, João Paulo de Martelli, Patrícia Benedini Gorgulho, Honória de Fátima Abstract in English: The present study describes phenol adsorption on commercial active carbon (CAF) under alkaline conditions in the concentration range of 0.01 to 2.08 mmol L-1. Surface characterization has been performed by means of surface area measurements, IR spectroscopy and Boehm titration. The effect of temperature on the adsorption equilibrium isotherm was investigated at 23, 30, 40, 50 and 60 °C. The results showed that adsorption capacity decreased with increasing temperature. The adsorption kinetics and the role of surface characteristics on the adsorption of phenol also discussed. |
Artigo Annual variations of methylxanthines in Ilex paraguariensis A. St.-Hil (maté) samples in Ijui and Santa Maria, State of Rio Grande do Sul Schubert, Alexandre Zanin, Francisco Fernandes Pereira, Danielle Fontana Athayde, Margareth Linde Abstract in English: Ilex paraguariensis is a native plant in Southern Brazil, whose leaves are utilized in beverages such as chimarrão and tererê. This study investigated variations of total methylxanthines in leaves from two Ilex populations collected at one-month intervals over the course of one year. The levels varied from 1.92 to 10.37 mg/g (Ijuí) and 1.77 to 9.17 mg/g (Santa Maria). Statistical analysis indicated a significative variation in the contents of all samples analysed, confirming seasonal fluctuations. These results show that the period of harvest might decisively influence the organoleptic characteristics of raw material used in industry and therefore in commercial products. |
Artigo Turbidimetric determination of homatropine methylbromide in pharmaceutical formulations using a flow injection analysis system Canaes, Larissa S. Fatibello-Filho, Orlando Abstract in English: A flow injection turbidimetric procedure exploiting merging zones is proposed for determining homatropine methylbromide (HMB) in pharmaceutical preparations. The determination is based on the precipitation reaction of homatropine methylbromide with AgNO3 solution to form a precipitate, which was measured at 410 nm. The analytical curve was linear in the HMB concentration range from 8.0x10-4 to 1.7x10-3 mol L-1, with a detection limit of 9.5x10-5 mol L-1. The recoveries ranged from 94.9 to 104 %, the sampling frequency was 75 h-1 and relative standard deviations were smaller than 2.0 % for solutions containing 1.2x10-3 and 1.5x10-3 mol L-1 HMB (n=10). The results obtained for commercial formulations using the FIA procedure were in good agreement with those obtained by using a comparative method (r= 0.9983). |
Artigo Chemical constituents of trunk bark of Amburana cearensis A.C. Amith Canuto, Kirley Marques Silveira, Edilberto Rocha Abstract in English: The phytochemical analysis of the ethanol extract trunk bark of Amburana cearensis allowed the isolation and identification of twelve constituents: coumarin, sucrose, two phenol acids (vanillic acid and protocatechuic acid), five flavonoids (afrormosin, isokaempferide, kaempferol, quercetin and 4'-methoxy-fisetin), a phenol glucoside (amburoside A) and a mixture of glucosilated b-sitosterol and stigmasterol. Their structures were elucidated by spectroscopic methods such as IR, MS, ¹H and 13C NMR, including uni and bidimensional techniques, in addition to comparison with literature data. |
Artigo Thermogravimetric study of the effect of temperature and atmosphere on sulfur dioxide absorption by limestone Ávila, Ivonete Crnkovic, Paula M. Milioli, Fernando E. Abstract in English: Thermogravimetry was applied to investigate the effects of temperature and atmosphere on conversion of sulfur dioxide (SO2) absorbed by limestone. Ranges of temperature and particle size were studied, typical of fluidized-bed coal combustion. Isothermal experiments were performed at different temperatures (between 750 and 950 ºC) under local atmospheric pressure (~ 697 mmHg) in dynamic atmospheres of air and nitrogen. The maximum conversion was 29% higher in nitrogen atmosphere than in air atmosphere. The optimum conversion temperature was found at 831 ºC in air atmosphere and at 894 ºC in nitrogen atmosphere. |
Artigo Chemical constituents and antioxidant activity of Sida galheirensis Ulbr. (Malvaceae) Silva, Davi Antas e Silva, Tânia Maria Sarmento da Lins, Antônio Cláudio da Silva Costa, Danielly Albuquerque da Cavalcante, José Marcílio Sobral Matias, Wemerson Neves Souza, Maria de Fátima Vanderlei de Braz Filho, Raimundo Abstract in English: The phytochemical investigation of Sida galheirensis led to the isolation of 5,4'-dihydroxy-3,7,3´-trimethoxyflavone, 17³-ethoxyphaeoforbide, a rare natural product, 6,7-dimethoxycoumarin, ortho-hydroxybenzoic acid, sitosterol-3-O-beta-D-glucopyranoside, stigmasterol-3-O-beta-D-glucopyranoside, 5,7,4'-trihydroxyflavone, 5,7,3',4'-tetrahydroxyflavone, kaempferol-3-O-beta-D-(6"-E-p-coumaroyl) glucopyranoside and luteolin 7-O-beta-D-glucopyranoside. Their structures were assigned based on spectroscopic analyses, including two-dimensional NMR techniques. Antioxidant activities of hexane, CHCl3, EtOAc, BuOH and EtOH extracts of Sida galheirensis were measured using the 1,2-diphenyl-2-picryl-hydrazyl (DPPH) free radical scavenging assay. This is also the first work reporting the chemical investigation of Sida galheirensis. |
Iron oxide and pyrocatechol: a spectroscopy study of the reaction products Barreto, Wagner José Barreto, Sônia Regina Giancoli Moreira, Ivanira Kawano, Yoshio Abstract in English: The reaction of 1,2-dihydroxy-benzene (pyrocatechol) (C6H6O2) with iron oxide (Fe2O3) and sodium thiosulfate (Na2S2O3) in aqueous medium (pH 7) was investigated. Pyrocatechol suffers autoxidation and coordinates with Fe3+ in solution. The presence of S2O3(2-) in solution was fundamental to generate and stabilize the pyrocatechol oxidation products as o-semiquinones. This compound was isolated and its structure characterized using FT-IR, EPR and UV-Vis Spectroscopy as [CTA][Fe(SQ)2(Cat)]. A thermal mass loss mechanism was proposed based on Thermogravimetric Analysis (TG) to support the structural characterization. |
Artigo A novel synthesis of alpha-bromoacetophenones and its application in obtaining 2-benzoylbenzofuranes Azevedo, Mariangela S. Alves, Ana Paula L. Alves, Glaucia B. C. Cardoso, Jari N. Lopes, Rosângela S. C. Lopes, Cláudio C. Abstract in English: alpha-Bromoacetophenones are important in organic synthesis. They have been widely used as precursors of several natural products. Several methods of bromination aiming at their synthesis have been described, however they furnish a mixture of starting material 10, mono 8 and dibromide 11 products. We developed a novel, simple and efficient synthesis of these compounds with applications in the synthesis of benzoylbenzofurans 9, compounds with important pharmacological properties, such as the ability of dilating the coronary artery and analgesic action. Such compounds have also been used as key intermediates to obtain quinone systems. |
Vibrational contribution to dipole polarizability and first hyperpolarizability of LiH Costa, Marcello F. Ribeiro, Mauro C. C. Abstract in English: The role played by electron correlation and vibrational correction on the polarizability of the LiH molecule is demonstrated. We present results for the dipole moment, polarizability and first hyperpolarizability of the LiH molecule obtained through many-body perturbation-theory, coupled-cluster and quadratic configuration interaction methods. Our best result for the dipole polarizability, obtained using the QCISD(T) scheme, indicates that the vibrational contribution is appreciable, amounting to ca. 10% of the total polarizability. Regarding the first hyperpolarizability, the vibrational contribution is even more important and has opposite sign in comparison with the electronic contribution. |
Myoglobins: the link between discoloration and lipid oxidation in muscle and meat Møller, Jens K. S. Skibsted, Leif H. Abstract in English: Aerobic metabolism changes rapidly to glycolysis post-mortem resulting in a pH-decrease during the transformation of muscle in to meat affecting ligand binding and redox potential of the heme iron in myoglobin, the meat pigment. The "inorganic chemistry" of meat involves (i) redox-cycling between iron(II), iron(III), and iron(IV)/protein radicals; (ii) ligand exchange processes; and (iii) spin-equilibra with a change in coordination number for the heme iron. In addition to the function of myoglobin for oxygen storage, new physiological roles of myoglobin are currently being discovered, which notably find close parallels in the processes in fresh meat and nitrite-cured meat products. Myoglobin may be characterized as a bioreactor for small molecules like O2, NO, CO, CO2, H2O, and HNO with importance in bio-regulation and in protection against oxidative stress in vivo otherwise affecting lipids in membranes. Many of these processes may be recognised as colour changes in fresh meat and cured meat products under different atmospheric conditions, and could also be instructive for teaching purposes. |
Revisão Ethnopharmacological, biological and chemical aspects of the Cassia genus Viegas Junior, Cláudio Rezende, Amanda de Silva, Dulce Helena Siqueira Castro-Gambôa, Ian Bolzani, Vanderlan da Silva Barreiro, Eliezer J. Miranda, Ana Luisa Palhares de Alexandre-Moreira, Magna Suzana Young, Maria Cláudia Marx Abstract in English: Species of Cassia are widely distributed in tropical and subtropical regions throughout the world, and have been extensively investigated chemically and pharmacologically.They are known to be a rich source of phenolic derivatives, most of them with important biological and pharmacological properties. Some Asian, African and Indian tribes use these species as a laxative, purgative, antimicrobial, antipyretic, antiviral and anti-inflammatory agent. Among a number of other classes of secondary metabolites, such as anthracene derivatives, antraquinones, steroids and stilbenoids, biologically active piperidine alkaloids are an especially important bioactive class of compounds that showed to be restricted to a small group of Cassia species. In this paper we present an overview of the chemical, biological and ethnopharmacological data on Cassia piblished in the literature. |
Revisão Secundary metabolites from species of Anacardiaceae Correia, Suzimone de J. David, Juceni P. David, Jorge M. Abstract in English: This review describes some aspects of the family Anacardiaceae dealing with the presence and distribution of secondary metabolites in the main genera of this family and their biological activities. It reports the occurrence of different natural compounds present in their species with special emphasis on phenolic lipids, flavonoids and triterpenes that are typical metabolites of this family. |
Revisão Synthetic approaches to amidines Santos, Maurício Silva dos Bernardino, Alice Maria Rolim Souza, Marcos Costa de Abstract in English: The amidine functional group is found in a wide range of natural products and is biologically active against several pathogens. In addition, amidines have long been regarded as useful intermediates in the synthesis of heterocyclic compounds. Consequently, a great number of methods have been developed for the preparation of amidines. Pinner's method is the most commonly used. Conventional methods include: - the addition of metal amides or amines to nitriles, the addition of amines to imido esters and the condensation of amides with amines in the presence of halogenating reagents. In this report, the main methods for synthesis of amidines will be described. |
Revisão Prodrug activation by enzyme, a promising strategy for chemotherapy Blau, Lorena Menegon, Renato Farina Chung, Man Chin Abstract in English: Strategies that promote selective activation of prodrugs by enzymes can be divided into two major classes: 1) deliver of a monoclonal antibody-enzyme immunoconjugate that can recognize a specific antigen and promote the prodrug to a citotoxic drug, with a high selectivity for the target cells, and 2) selective gene delivery encoding an enzyme that can promote the prodrug to a citotoxic drug for the target cells. In this article are discussed ADEPT (antibody-directed enzyme prodrug therapy), GDEPT (gene-directed enzyme prodrug therapy), VDEPT (virus-directed enzyme prodrug therapy), GPAT (genetic prodrug activation therapy) and PDEPT (polymer-directed enzyme prodrug therapy) approaches, their clinical trials, advantages, disadvantages and perspectives. |
Revisão Electrochemical sensors: fundamentals and applications in microenvironments Lowinsohn, Denise Bertotti, Mauro Abstract in English: Electrochemical sensors have attracted considerable attention in recent years because they provide data about the chemical state of our surroundings and the dynamics of the chemical transformations in the form a spatially resolved image. Particular interest has been directed to measurements in restricted-volume samples as new technologies enable the fabrication of miniaturized versions of sensors with reproducible characteristics. Taking these aspects into consideration, this review focuses on the use of electrodes of micrometer dimensions to acquire chemical information in microdomains in which concentrations may not be spatially homogeneous. This is possible because microelectrodes allow fast-response measurements with micrometer resolution to be performed. On the other hand, the use of microelectrodes as amperometric sensors presents an inherent drawback owing to the insufficient specificity toward the substrate of interest. Hence, some comments on strategies to enhance the selectivity of amperometric sensors are also made. Finally, recent applications of structurally microscopic electrodes as in vivo sensors are shown, as well as a prospect of the future trend in this field. |
Revisão Polypeptides and proteins that influence beer foam quality and analytical methods used in their study Silva, Filipe Ferreira, Isabel M. P. L. V. O. Teixeira, Natércia Abstract in English: A review of polypeptides and proteins that influence, direct or indirectly, beer foam quality, as well as the most relevant analytical methods used in their study, are presented. Protein Z, LTP1 and hordein/glutelin fragments originated from malt have a direct influence on beer foam quality. Other proteins, like malt hordeins and albumins and wheat puroindolines, are, to some degree, also important for beer foam quality. Protein hydrophobicity is pointed out as a key parameter to enhance foam quality. Electrophoretic, chromatographic and immunological analytical methods are currently used to study polypeptides and proteins present in barley, malt, wort, beer, and foam. Best results are obtained when combinations of these methods are applied. |
Revisão Aqueous biphasic systems: an efficient alternative for extraction of ions Silva, Maria do Carmo Hespanhol da Silva, Luis Henrique Mendes da Paggioli, Fernanda Jürgensen Coimbra, Jane Sélia Reis Minim, Luis Antonio Abstract in English: Solvent extraction has been successfully applied to metal ion preconcentration and often meant the use of toxic organic diluents. However, regulatory pressure is increasingly focusing on the use and disposal of organic solvents, and thus the development of nonhazardous alternatives is important. In this review, we examine the application of aqueous biphasic systems (ABS) to extraction of ions, analyzing their potential and limitations and suggest that ABSs could be an efficient substitute for oil/water biphasic systems. ABSs are formed by mixing certain inorganic salts and water-soluble polymers, or by mixing two water-soluble polymers. |
Divulgação Oxidative stress, genome lesions and signaling pathways in cell cycle control Berra, Carolina M. Menck, Carlos F. M. Di Mascio, Paolo Abstract in English: The generation of reactive oxygen species (ROS) may be both beneficial to cells, performing functions in intracellular signaling and detrimental, modifying cellular biomolecules. ROS can cause DNA damage, such as base damage and strand breaks. Organisms respond to chromosome insults by activation of a complex and hierarchical DNA-damage response pathway. The extent of DNA damages determines cell fate: cell cycle arrest and DNA repair or cell death. The ATM is a central protein in the response to DNA double-strand breaks by acting as a transducer protein. Collected evidences suggest that ATM is also involved in the response to oxidative DNA damage. |
Divulgação Aqueous two-phase systems: fundamentals and applications for partitioning/purification of proteins Silva, Luis Henrique Mendes da Loh, Watson Abstract in English: By the year 2005 the world biochemical market will reach an estimated $ 100 billion and separation processes are a vital link between lab discoveries and the fulfillment of this commercialization potential. The practical application of aqueous two-phase systems (ATPS) to extraction processes has been exploited for several years for the recovery of biological products. Unfortunately, this has not resulted in an extensive presence of the technique in commercial processes. In this paper a critical overview of the fundamental thermodynamic properties related to formation of aqueous two-phase systems and their application to extraction and purification of bioparticules is presented. |
Divulgação Oxidative damage and neurodegeneration: what have we learned from transgenic and knockout animals? Barbosa, Lívea Fujita Medeiros, Marisa H.G. de Augusto, Ohara Abstract in English: Accumulated evidence indicates that oxidative stress plays a role in neurodegenerative diseases, such as Alzheimer, Parkinson and Amyotrophic Lateral Sclerosis. Here, we emphasize the results provided by the technology of genetically modified animals. Studies with transgenic and knockout mice have allowed great advances in the research of oxidative stress in general and in the central nervous system, and are pointing to potential targets for the development of new drugs and therapies to disrupt the cycle of events that lead to neuronal death. Thus, genetically modified animals are a valuable tool for the comprehension of human diseases, including neurodegenerative ones. |
Divulgação Optogalvanic spectroscopy: some relevants aspects Pereira, Robson Valentim Pessine, Francisco B. T. Abstract in English: In this work we present the optogalvanic effect in ionized gases in an historical perspective. This effect was observed for the first time by Foote and Mohler in 1925, and explained by Penning in 1928 for mixtures (Ne-Ar) and pure gases (or vapours) in 1937. Also, we show some aspects of the contributions of Romenian authors for the development of optogalvanic spectroscopy, which was used as a new technique only after 1964. |
Divulgação Toxicological and chemical aspects of Anatoxin-a Rodríguez, Vania Moura, Sidnei Pinto, Ernani Pereira, Claudio M. P. Braga, Rodolpho Campos Abstract in English: Anatoxin-a and its analogues are azabicyclic alkaloids that represent one of the most powerful nicotinic agonists known for the nicotinic acetylcholine receptor (nAChR). Because of this potent mechanism of action, anatoxin-a and its derivatives represent a target for the discovery of novel drugs. Their syntheses are useful for environmental monitoring and also for pharmacokinetic/pharmacodynamic and toxicological studies. Some strategies for the synthesis of anatoxin-a and analogous compounds are described herein, covering the period from 1996 to the present date. In this review, emphasis is given to the chemical and toxicological aspects of some variants of anatoxin-a, including homoanatoxin-a and anatoxin-a(s). |
Nota técnica Study of recovery and stability of derivatized gliphosate and AMPA in soil using national resins Souza, Tomaz Alves de Matta, Marcia Helena de Rizzo da Montagner, Émerson Abreu, Adley Bergson Gonçalves de Abstract in English: In the present paper we studied the recoveries of glyphosate, N-(phosphonomethyl)glycine (GLY) and its major metabolite, (aminomethyl)phosphonic acid (AMPA) in soil using national (Brazilian) ion-exchange resins, derivatization by a mixture of trifluoroacetic anhydride and trifluoroethanol and analyses by GC-MS. The quantification limits were 12 ng.g-1 for both compounds and the methodology showed a range of recuperation from 85 to 94% with coefficients of variation (CV) ranging from 4.07 to 6.91% for GLY. For AMPA, the mean recoveries ranged from 87 to 102% with CVs ranging from 5.81 to 6.99%. Additional studies showed that, due to the instability of the derivatized compounds, they must be analysed keeping constant time between derivatization and analysis, preferably less than 24 h. |
Nota técnica Utilization of a conventional CRT monitor as a high voltage power supply for capillary electrophoresis Silva, José Alberto Fracassi da Frasatto, Leonardo Abstract in English: This article describes the use of a conventional CRT monitor as a high voltage power supply for capillary electrophoresis. With this monitor, a 23-kV high voltage with a ripple of 1.32% was observed. The reproducibility of the applied high voltage was evaluated by measuring the standard deviations of peak area and migration time for five consecutive injections of a test mixture containing potassium, sodium, and lithium cations at 50 mmol L-1. The errors were about 2.5% and 0.6% for peak area and migration time, respectively. The maximum current tested was about 180 mA, which covers most capillary electrophoresis applications. This system has been successfully used for several months, maintaining the desired level of performance. |
Educação A proposal for the teaching of Qualitative Analytical Chemistry Abreu, Daniela Gonçalves de Costa, Carla Regina Assis, Marilda das Dores Iamamoto, Yassuko Abstract in English: In recent years, because of the need for a more flexible curriculum established by the Curriculum Guidelines of the National Brazilian Education (law 9394/96), the pedagogical project of the Chemistry course of FFCLRP/USP has undergone alterations, amongst them the gradual reduction of the hours devoted to the discipline Qualitative Analytical Chemistry. In this context, this discipline has been carefully analyzed and reorganized in order to allow the elimination of redundancies and the introduction of activities considered important for the professional formation of both chemists and chemistry teachers. In this work, we will discuss the main strategies adopted in this reorganization with the objective of making the teaching/learning process more dynamic and efficient. |
Educação The formation of chemistry post-graduate students for teaching in higher education Arroio, Agnaldo Rodrigues Filho, Ubirajara Pereira Silva, Albérico Borges Ferreira da Abstract in English: The article presents a brief analysis on chemistry post-graduate students' perception on teaching in higher education. This study was done based on the context of students' formation in chemistry post-graduate programs and makes suggestions on how to improve the formation process of post-graduate students in order to decrease the rupture between teaching and research in chemistry post-graduate programs. |
Assuntos gerais From the thermoscope to the digital thermometer: four centuries of thermometry Pires, Denise Prazeres Lopes Afonso, Júlio Carlos Chaves, Francisco Artur Braun Abstract in English: This work describes the evolution of temperature measurement in the last four centuries using thermometers based on the thermal expansion of liquids such as ethyl alcohol and mercury. The concept of temperature was strongly dependent on the researcher and there was no systematic temperature scale for universal use. The precursor of the common thermometer was the thermoscope, probably invented at the end of the XVIth century. In the XVIIIth century the instrument was greatly improved and several thermometric scales were proposed some of which have been in use until now. These scales were based on arbitrary points. Mercury and ethyl alcohol were the most employed thermometric fluids. In the XIXth century, the concept of absolute zero was a great advance in this field. The most important contribution during the XXth century was the establishment of international temperature scales. The design of the thermometer has been essentially the same along the last 300 years, but many models were proposed for industrial and research purposes. Its association with the densimeter was of great importance for control of industrial chemical processes and also for teaching purposes in the past. Nowadays, there is a clear tendency to replace mercury-based thermometers by electronic digital models. Thermochemistry is the natural relationship between temperature and chemistry. |
Assuntos gerais 25 years of chemometrics in Brazil Barros Neto, Benício de Scarminio, Ieda S. Bruns, Roy E. Abstract in English: Chemometric activities in Brazil are described according to three phases: before the existence of microcomputers in the 1970s, through the initial stages of microcomputer use in the 1980s and during the years of extensive microcomputer applications of the ´90s and into this century. Pioneering activities in both the university and industry are emphasized. Active research areas in chemometrics are cited including experimental design, pattern recognition and classification, curve resolution for complex systems and multivariate calibration. New trends in chemometrics, especially higher order methods for treating data, are emphasized. |