Resumo em Inglês:

Nanopore has developed into an indispensable tool for single molecules experiments, where useful information about the characteristics of DNA/RNA can be obtained from the flowing of ionic current elicited by individual molecules as they traverse a single nanometer-scale aperture. However, due to the relatively high background current noise and low measurement bandwidth, it is difficult to distinguish the molecule-specific signals from the intrinsic noises of the nanopore recording systems, which impeded its application in DNA sequencing. In this paper, we present a novel consensus filter-based noise reduction approach, which considerably improves the accuracy of the noise-filtered current traces and the signal-to-noise ratios (SNRs). The new approach is compared to the conventional Bessel filters and validated by analyzing simulated representative translocation data as well as alpha-Hemolysin (α-HL) nanopore experimental data. It is demonstrated that the high frequency noise generated by the voltage noise of the amplifier and Analog-to-Digital converter circuits (ADC) can be significantly reduced and some hidden short-lived translocation events can be recovered with satisfying accuracy beyond the conventional limitations of the Bessel filters.

Resumo em Inglês:

The inhibition effect of limonene on the organisms involved in anaerobic reactors may affect obtaining H2 in this process. Rapid and precise limonene quantification is desirable to characterize wastewaters. The objective of this research was to develop a Gas Chromatography Coupled to Mass Spectrometry (GC-MS) method to determine limonene concentration in liquid samples from batch reactors applied to H2 production at 30 ºC. Method validation was carried out through calibration curves (3 to 20 mg L-1of limonene), in addition to evaluating its precision (CV =0.1%), linearity (R2=0.979), limits of detection (1.7 mg L-1) and quantification (4.2 mg L-1). Its inhibitory effect was evaluated with increasing concentrations of limonene (without addition to 2000 mg L-1). Limonene affected the starting time of H2 production (λ), since λ was 8.7 h in control assays and 15 h with 2000 mg L-1 of limonene. The same was observed for obtaining H2, since 19.5 mmol H2 L-1 was obtained in control assays and 8.7 mmol H2 L-1 was obtained in assays with 2000 mg L-1 of limonene. This method was effective for limonene determination in liquid samples from batch reactors and could be used for characterization and control of anaerobic reactors.

Resumo em Inglês:

The primary objective of this study was to investigate the binding of buddleoside to bovine serum albumin (BSA) by different analytical techniques. The analytical principles of affinity capillary electrophoresis (ACE) and fluorescence spectroscopy used in the experiments were different. Mobility (M) that is independent of viscosity of the operating buffer and voltage was chosen to eliminate the effects of electroosmotic flow (EOF) in ACE and was applied to estimate the binding constant Ka. The quenching constant Ksv, binding site number n and binding constant Kb were provided by the fluorescence quenching method. After data analysis of the fluorescence quenching process, it can be seen that the quenching of BSA by buddleoside is a static quenching method. The binding constants between buddleoside and BSA obtained from ACE and fluorescence spectra were 1.218×105 and 1.1915×105, respectively. According to the thermodynamic parameters of ΔG, ΔH and ΔS, it can be inferred that Van Der Waals force and hydrogen bonding force exist in the interaction between buddleoside and BSA. This study can provide a reference for the study of the transport and function mechanism of buddleoside in vivo.

Resumo em Inglês:

Determining the morphological distribution of hydrogen atoms in calcium silicate hydrate phase (C-S-H) is of great concern but challenging. In this work, based on the stoichiometric composition of (CaO)1.7(SiO2)(H2O)1.8, a series of amorphous Ca1.7•Si•(O)3.7-x•(OH)2x•(H2O)1.8-x models are constructed using Monte Carlo method, where x represents the molar number of dissociated H2O molecules (x∈0~1.8). A molecular dynamics simulation has been performed with the ClayFF force field. The analysis of Qn, radial distribution function (RDF), coordinate number (CN), mean chain length (MCL), mean square displacement (MSD), elastic modulus (M), and Young’s modulus (E) are used to explore the microstructure, hydrogen atom distribution and mechanical properties. The results demonstrate that the proportions of hydrogen atoms in Ca-OH, Si-OH, and H2O are about 26%~45%, 13%~22%, and 61%~33%, respectively. The calculated microstructure parameters and mechanical properties, especially for C-S-H models with x of 0.7~1.2, are in good agreement with those reported previously in theoretical and experimental works, indicative of the excellent rationality of our theoretical C-S-H models. The simulated results of this work provides a new strategy of constructing theoretical C-S-H model, which might be suitable for studying the doping behavior of metal oxides or metal salts in C-S-H.

Resumo em Inglês:

Two methodologies were developed to monitor the biodiesel content of mafurra in mixtures with diesel using hydrogen nuclear magnetic resonance (1H NMR) Spectroscopy combined with the multivariate regression by orthogonal projections to latent structure (OPLS) and partial least squares (PLS). The efficiency of these methodologies was analyzed based on the figures of merit and the fit of the models through the correlation of the measured and predicted values of the calibration and prediction sets. The results of the figures of merit in the OPLS model were better than in the PLS model. A high correlation between the measured and predicted values was evident in the OPLS model, with a correlation coefficient (R2) greater than 0.99, demonstrating a better fit of the OPLS model in relation to the PLS model which presented a correlation coefficient (R2) less than 0.98. The OPLS model is more robust and has good predictive capacity than the PLS model because it obtained a higher Q 2 value. The excellent results of the application of 1H NMR spectroscopy combined with multivariate regression by OPLS suggest that this analytical methodology is ideal, feasible, efficient and suitable for use by inspection agencies to control the quality of this fuel.

Resumo em Inglês:

Most volatile organic compounds (VOC) have adverse effects on human health and the environment and react individually with different velocities and mechanisms to form ozone. The present work determined the concentration of 55 samples of benzene, toluene, ethylbenzene and xylenes (BTEX), an important subgroup of VOC, by active sampling with active carbon cartridge in the areas of Barra da Tijuca, Deodoro and Maracana between the months of December 2014 to September 2015. The samples were extracted with dichloromethane and analyzed by gas chromatography coupled to mass spectrometry (GC-MS). The percentage distribution of BTEX showed toluene as the most abundant compound in the three sites, with 54, 3% in Barra da Tijuca, 57, 4% in Deodoro and 38, 1% in the Maracana area of the total BTEX. The mean benzene/toluene (B/T) ratios were 0.12 (Maracana), 0.37 (Barra da Tijuca) and 0.23 (Deodoro), confirming the emission source as predominantly vehicular. Using reactivity scales, toluene was the compound that most contributed to the formation of ozone and benzene was less reactive than the others. The carcinogenic risk was considered indifferent in all sites.

Resumo em Inglês:

Copaiba oilresins present medicinal uses that demand the development of methodologies that could ensure the authenticity and guarantee the species differentiation. The usual way to differentiate the copaiba oils is analyze the terpene composition, mainly the diterpenic acids profile. Unlike caryophyllene and its oxide, copaiba diterpenes are not commercially available and lab obtention is expensive and time consuming. At this paper, a new methodology is presented that allows the fast and reliable detection of copaiba biomarkers using HPTLC retention factor relative to an appropriate standard. Several commercially available substances were analyzed and the monoterpene linalool oxide was chosen. The comparison of relative retention factors allowed the confirmation of caryophyllene and its oxides and the diterpenic acids copalic, hydroxy-copalic, acetoxy-copalic, agathic, and hardwickiic. Calibration curve showed strong correlation (│r│ ≥0.9962) with R2 ≥0.9928.

Resumo em Inglês:

Brown sugar and sticky rice were frequently used as organic additives in Chinese mortars. This study applied enzymatic spectrophotometric methods to identify sucrose and starch contents in traditional Chinese lime- and earth-based mortars. The focus was to understand and evaluate the qualitative detection capacity of enzymatic method in mortars, by first applying the method on a series of lab-prepared mortar specimens with specific amounts of brown sugar and sticky rice addition, then on historic mortar samples suspected to contain brown sugar and sticky rice. The potential contribution and limitations of enzymatic method in analysis of sucrose and starch in mortars was compared with other common available analytical methods. The results suggested that for lab-prepared brown sugar mortar specimens, enzymatic method was more sensitive and exclusive than chemical method, and particularly had higher detection capacity in lime mortars. For simulated mortars with sticky rice addition, enzymatic method showed no distinct detection capacity differences among the studied inorganic binders and comparing with chemical methods was more sensitive in earth-based mortars. Enzymatic analysis on historic mortar samples was able to distinguish some false-positive results from the chemical and FTIR analysis, which was then corroborated by SEM.

Resumo em Inglês:

Many instrumental techniques are used to monitor the quality of food products, highlighting near infrared spectroscopy (NIRS). In order to determine the authenticity of 60 commercial oil samples seized by the Espírito Santo state police, this work used a portable spectrometer in the NIR region associated with chemometric tools such as principal component analysis (PCA) and partial least squares regression (PLS) to classify and quantify possible adulterants present such as soybean oil. In addition, physicochemical tests (acidity, peroxide and ultraviolet absorption) were carried out on commercial samples. The PLS regression model built to quantify soybean oil showed a coefficient of determination (R2) greater than 0.99, showing itself to be satisfactory. The results showed that all samples analyzed had a high content of adulterant and cannot be classified as extra virgin olive oil.

Resumo em Inglês:

Modern agriculture relies on the massive use of agrochemicals, including herbicides. Despite their effectiveness, a continuous use of herbicides sharing the same target has resulted in the selection of weed biotypes resistant to such chemicals. To cope with this problem, the development of new herbicides is an urgent requirement. In this work we applied the Active compound Derivatization Method (ADM) strategy to develop a new tetraoxane (5), derived from the synthetic auxin 2-(naphtalen-1-yl)acetic acid (NAA). Greenhouse bioassays showed that 5 caused chlorosis, necrosis and leaf epinasty in Cucumis sativa. Furthermore, this compound, at the concentration of 1.25 x 10-5 mol L-1, inhibited the growth of important weeds such as Bidens pilosa, Iponomea acuminate, Solanum americanum and Althernantera ficoidea. For some weeds, the compound effect was higher or comparable to those caused by commercial glyphosate and imazethapyr. In addition, degradation studies revealed that 5 is transformed into NAA. The results also showed that 5 could act as photosynthesis inhibitor and as an auxin herbicide. In summary, we have discovered a new compound that may be a useful lead for the development of a commercial herbicide.

Resumo em Inglês:

Turmeric (Curcuma longa L.) is a medicinal plant that is cultivated worldwide. This study was conducted to evaluate the variability in the percentage and the chemical composition of volatile oils from 12 turmeric samples. Rhizomes of the turmeric plant were collected from three different producers in the Brazilian like savanna (Cerrado) habitat in the state of Bahia. The chemical composition of the oils derived from the rhizomes was analysed by thin-layer chromatography and GC-MS. The average oil content was 3.97% ± 0.61%, varying from 3.0% to 5.16%. There were differences between producers; however, all samples met the specification of the Brazilian Pharmacopoeia. Thin-layer chromatographic analysis revealed qualitative similarity in both oil and curcuminoid components among the samples. The major components identified in the oils by gas chromatography were ar-turmerone (40.00% ± 13.20%), α-turmerone (10.05% ± 2.90%) and curlone (22.73% ± 12.72%). Regarding stability, there was a difference between the essential oil percentages after 6 months, but the content was maintained adequate and the chromatographic profile remained similar. The vegetable raw material obtained from C. longa rhizomes produced in the western region of the state of Bahia met the quality requirement of the Brazilian Pharmacopoeia.

Resumo em Inglês:

The recovery of precious and base metals of a metal concentrate from ground waste printed circuit boards (PCBs) is described in detail. Samples were treated with NaOHaq. to remove the soldering mask. Experiments were performed in acidic medium (HF, H2SO4, CH3COOH or H3PO4) using H2O2 as oxidant. Base metals were leached in high yields (>99 wt.%) at ~40 ºC after ~1 h (HF), ~2 h (H2SO4), ~4 h (H3PO4) and ~5 h (CH3COOH). Lead precipitated in the presence of H2SO4 and HF. Precious metals were not oxidized. Ceramic/fiberglass components were dissolved in the presence of HF. Silver, palladium and gold were recovered from the insoluble solid, in this order, by a sequential oxidative treatment in aqueous medium. Recovery of leached elements was possible by a combination of solvent extraction and precipitation. The choice of the extractant and the precipitant were essential to recover them with high yields. The leachates from H3PO4 + H2O2 experiments could not be processed above pH 2.5. Leaching of waste PCBs in the presence of a weak organic acid is possible but a multistage separation scheme for elements recovery is unavoidable as PCBs is a complex material in terms of composition.

Resumo em Inglês:

Food safety is a constant and necessary concern due to the worldwide increase of the food demand. The monitoring of quality parameters demands the development of accurate, easy and fast procedures. The aim of this work was to develop a cheap, miniaturized and trustworthy salting-out assisted liquid-liquid extraction (SALLE) procedure for the determination of pesticides in wines. Sample and acetonitrile were mixed and the addition of NaCl and CH3COONa were used for separation of aqueous and organic phases. After centrifugation, the organic phase was directly injected into a liquid chromatograph. The developed SALLE procedure consumed at least 25-fold less reagent compared to conventional QuEChERS procedure. Additionally, the d-SPE step of the QuEChERS method was suppressed, without efficiency losses. The developed procedure was compared to the conventional methodology and no significant difference was observed. It was successfully applied to the determination of three pesticides in wines by liquid chromatography. Low consumption of sample and solvent, low residues generation, simple instrumentation are notable advantages. The suppression of the d-SPE step simplified the process and the risk of analyte losses.

Resumo em Inglês:

This review briefly describes the evolution of organometallic chemistry and photoredox catalysis as independent fields; followed by a more in-depth presentation and discussion of representative examples derived from their synergistic combination, which generally leads to powerful cross-coupling protocols. In this context, the rational deconvolution of these complex catalytic systems into their isolated, more simple components are evaluated in order to understand their properties and reactivities.

Resumo em Inglês:

Itaconic acid (IA) is a very promising platform molecule due to the possibility of it being used to obtain products such as methyl methacrylate and synthetic latex, with the prospect that its global market will grow at an average annual rate of 2.8% (CAGR) from 2021 to 2026, exceeding US$ 116.6 million in sales. The main technological route used to obtain itaconic acid is fermentation using different strains of Aspergillus terreus fungi. The main advancements are related to genetic engineering, as Aspergillus terreus is the most tolerant of the microorganisms employed in the process synthesis and optimization. The main substrate used is glucose (52%), followed by glycerol (25%). Among the results presented in this paper, the best production was achieved using Ustilago maydis, with 220 g L-1 of IA, yielding 0.33 g g-1, using glucose as a carbon source. Moreover, it is necessary to continue optimizing the biological process of IA production, since it is a platform molecule with major economic potential.

Resumo em Inglês:

Stability is an important parameter to evaluate the quality, safety and efficacy of drug substances and pharmaceutical products. The stability studies aim to determine the ability of a formulation to maintain its specifications, in order to establish shelf life and recommended storage conditions. Despite the extensive relevance, until the 1980’s the stability assessment methods complied with technical and scientific principles without the intervention of regulatory acts by health authorities. The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) establishment in the 1990’s boosted the regulation on this issue, not only in the attended countries, but worldwide. In the Brazilian context, the first regulatory norm for stability studies was published in 2002 and it implied the requirement of the submission of a stability report for the sanitary registration of medicines. The development of the Brazilian legislation resulted, among other factors, from the progress of the analytical methods that have become increasingly efficient, sensitive and selective, which allows the achievements of results with greater accuracy and speed; and the use of modern techniques of solid form characterization, which provide important information about the stability of active ingredients and pharmaceutical products.

Resumo em Inglês:

Was supposed a numerical relationship between atoms of Hydrogen and Carbon in a hydrocarbon, assumption valid for all types of chains. In the proposed equation, variables such as number and types of carbon bonds are present, as well as the possible cycles. It was shown that the equation reduces to the known “general formulas” when applied to the type of chain in question. There is also a generalization of the equation to include elements of the group 16 (6A) of the Periodic Table, expanding its application to the molecules containing functional groups of this elements (we used functional groups containing oxygen as examples). This application generates an equation for each functional group, in an effort to study them algebraically; this effort points to the objective of the article, which is to provide algebraic foundations for the countable properties in chemical bonding. Finally, possible generalizations of the equation were mentioned, pointing out ways to be followed by those who are interested in this new subject. Even though it was done as a pure science research, it is easy to ignore non-interesting variables and introduce new interesting ones.

Resumo em Inglês:

Chemistry teacher training courses have been undergoing restructuring, encouraged by changes in legislation and various research in the educational area. This work presents an overview of the regulations, which in recent years has been considering the importance of including reflective practices during initial training courses, by increasing the workload of internships and the implementation of the “Practice as a Curricular Component” (Prática como Componente Curricular). In the light of these regimentation, through a documentary analysis, we investigate aspects related to the structure of the teacher education curriculum in two undergraduate chemistry courses, which are presented as courses with different curriculum structures, especially the percentage of hours devoted to specific activities that differentiate from the bachelor’s degree for the course as a whole and the distribution of these activities over the 4 years of the course. We identified resistance in change the structure of the curriculum to disassociate the teacher training courses from the baccalaureate. It was also investigated the profile of teachers for both institutions, which are similar and show that the majority of teachers have a bachelor profile, raising a question about the training of teacher educators.

Resumo em Inglês:

Inscriptions - graphs, diagrams, photographs, tables, and so forth - are central to scientific practice. In this study, a semiotic model was used to evaluate the reading of inscriptions by undergraduate chemistry students when giving oral presentations based on original research articles about environmental chemistry. Results revealed that the model helps to identify the extension of the adequacy of using inscriptions by the students in communicative situations. Potentialities and limitations of the model for chemistry education are discussed.

Resumo em Inglês:

Tuberculosis still is the world’s leading cause of death from a single infectious agent and has affected approximately 10 million people in 2018. The development of new technologies for treating tuberculosis is among the priority goals for the global fight against the disease. The present work makes a technological prospecting from patent documents, aiming to identify new technologies developed for the treatment of the disease, analyzing the most promising trends. The identification of new technologies was carried out through the Orbit Intelligence portal using the sentence: “(+ tuberculosis +) / TI / AB AND (A 61K OR A 61P) / IPC AND PRD> =2015” as a search strategy. We identified 41 patent families with experimental evidence (in vitro / in vivo) of efficacy against Mycobacterium tuberculosis, including resistant strains. The new technologies mainly consist of chemical synthesis products. The patent protection was demanded in countries with promising markets, with potential licensors and strong intellectual property regulations. The use of patents as a source of information can contribute to orientate the development of new drugs for tuberculosis.