Resumo em Inglês:

Poly (3-hydroxybutyrate) (P(3HB)) is the most studied thermoplastic biopolymer belonging to the polyhydroxyalkanoate (PHA) family, the main features of which include rapid biodegradability and biocompatibility. The bioplastic recovery process is an important step during production and can directly influence the characteristics of PHAs. However, more efficient methods for the production of P(3HB) are necessary to make it economically viable. The aim of the present study was to improve the standard, chloroform-based, extraction step for the recovery of P(3HB). The polymer was produced using a Ralstonia solanacearum strain. The following parameters were improved in the recovery process: heating time, separation method (filtration or liquid-liquid phase separation), biomass state (fresh or dry cell concentrate) and the solvent:biomass ratio. By improving the chemical extraction of P(3HB) we recovered 98% of the cumulative polymer and reduced the heating time by 75%. Furthermore, we improved the separation process and developed an extraction solution that was faster and more economical.

Resumo em Espanhol:

Biological activities from polyurethanes (PUs) synthesized from polyols (derived from castor oil) and isophorone diisocyanate were evaluated. In vitro degradability was evaluated by phosphate buffered saline (PBS) and antibacterial degradation with Escherichia coli and Pseudomonas aeruginosa. The biocompatibility was analyzed by: i) the antimicrobial activity against E. coli, S. aureus and P. aeruginosa, and ii) in vitro cytotoxicity assays using mouse embryonic fibroblast cell line L-929 in direct contact with the PUs and with NIH/3T3 cells in indirect contact with the PUs degradation products. PUs with polyol P1 (2,64% molar relation of pentaerythritol and castor oil) was the material with better biodegradation properties: 1.125±0.110% in 72 h by PBS at 100 ºC. In general, all materials were degraded up to 1.000±0.223% and 2.251±0.010% in 72 h by E. coli and P. aeruginosa, respectively. On the other hand, it was determined a close relationship between functionality of polyol and bacterial inhibition. The antibacterial effect of the PUs decreased by 67% for E. coli, 55% for S. aureus and 56% for P. aeruginosa after 24 h. Chemical modification of castor oil did not generate a cytotoxic effect on the tested cell lines. The evaluated materials are suggested as candidates to obtain biomaterials due to their mechanical properties and biocompatibility presented in untransformed cells.

Resumo em Inglês:

Six known compounds, three peptide derivatives: cyclo-(tryptophyl-phenylalanyl) (2), diketopiperazine dimer WIN 64821 (3) and 3-hydroxy-15H-tryptophenaline (4), one adenine derivative: 2-hydroxy-6-N-isopentenyl-adenine (5), one phtalide derivative: 4-methoxyphtalide (1) and one benzoic acid derivative: 3-hydroxy-4-(1-hydroxy-1,5-dimethyl-hexyl) benzoic acid (6), were isolated from the ethyl acetate extract of the endophytic fungus Aspergillus versicolor associated with the Piper aduncum plant. Their structures were determined on the basis of detailed interpretation of 1 D and 2D NMR spectra and in comparison with works reported in the literature. This paper, in effect, deals with the first report of these compounds in A. versicolor.

Resumo em Inglês:

Molecular descriptors are being widely used in QSAR/QSPR studies in chemistry and drug designing as well as modeling of compounds. Different topological descriptors have been formulated to investigate the physio chemical properties and chemical reactivity of compounds. In this article we gave exact relations for first and second Zagreb index, hyper Zagreb index, multiplicative Zagreb indices as well as first and second Zagreb polynomials for some benzenoid systems.

Resumo em Inglês:

Epoxy resins are an important class of thermostable polymers, widely used in structural applications or as adhesives. However, the low fracture resistance is their main weakness in many applications. Due to this fact, this study aims to modify a polymer matrix based on a novolac epoxy resin with an organo siloxane (AMS). The final properties of cured epoxys resins are affected by the curing process and the coatings modified in this study with AMS and cured with acid catalyst presented greater resistance to thermal decomposition compared to that cured with Aradur, demonstrating a higher content of crosslinking in the siloxane polyether and the novolak epoxy resin chains. This epoxy matrix modified was used to prepare coatings whose films applied to 1020 steel surfaces presented a resistance of 1010 Ohm-cm-2. This resistance value is one order of magnitude greater than that of epoxy resins films modified by siloxanes in published studies, which demonstrates a potential economy in terms of maintenance costs of metal structures and machines used in power plants (UTE). To obtain the developed inks in pilot plant scale, it was used an aromatic polyamine as curing agent, characterizing the product obtained as an epoxy bi-component paint for commercial use.

Resumo em Inglês:

The experiments described in this paper tested the hypothesis whether iontophoresis applied on a chitosan nanoparticle formulation could combine the enhanced drug accumulation into the follicular casts obtained using iontophoresis and the sustained drug release, reducing dermal exposure, provided by nanoparticles. Results showed that even though iontophoresis presented comparable minoxidil targeting potential to hair follicles than passive delivery of chitosan-nanoparticles (4.1 ± 0.9 and 5.3 ± 1.0 µg cm-2, respectively), it was less effective on preventing dermal exposure, since chitosan-nanoparticles presented a drug permeation in the receptor solution of 15.3 ± 4.3 µg cm-2 after 6 h of iontophoresis, while drug amounts from passive nanoparticle delivery were not detected. Drug release experiments showed particles were not able to sustain the drug release under the influence of a potential gradient. In conclusion, the application of MXS-loaded chitosan nanoparticles remains the best way to target MXS to the hair follicles while preventing dermal exposure.

Resumo em Inglês:

In present times, the Brazil is in the middle of the largest pesticide consumers worldwide, which demands proper control of environmental contamination. This study evaluated herbicides, acaricide, insecticides and fungicides in water and sediment carried-out from Lageado Tacongava hydrographic basin, Rio Grande do Sul, Brazil. For analysis, a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe), and/or SPE (Solid-Phase Extraction) using HPLC (High Performance Liquid Chromatography) with MS (Mass Detector) was optimized. As result, the Linearity R2 > 0.99; Recuperation between 78 a 117%; and RSD < 20% for the 70 compounds simultaneously analyzed. The Acetamiprid, Azoxystrobin, Bendiocarb, Fenamidone, metribuzin, Pendimethalin, pyridaben, Thiophanate-methyl and Truflumizole found in water, and Acetamiprid, Azoxystrobin, Bendiocarb, boscalid and thiophanate-methyl in sediment, at concentrations from 0.1 µg kg-1 to 39.6 µg kg-1. Standard of pesticide residues in water and sediment studies are needed to evaluate such contamination. Regional samplings standard, as was done here, will be useful in a future water resources contamination mapping.

Resumo em Inglês:

In this work barium titanate (BT) and strontium titanate (ST) were prepared by Microwave-Assisted Hydrothermal (MAH) method, using a Ti precursor different from those shown in the literature and various concentrations (1, 3 e 6 mol L-1) of KOH mineralizer. As a titanium precursor, an anatase complex with hydrogen peroxide were used. For the precursors of barium and strontium, chlorides were used. The materials resulting from the synthesis processes were characterized in room temperature by different techniques as like: X-Ray Diffraction (XRD), micro-Raman Spectroscopy, UV-Vis, Scanning Electron Microscopy (SEM) and Photoluminescence (PL). The results show that there were differences in crystallinity, morphology, number of phases and photoluminescence depending on the concentration of the mineralizer.

Resumo em Inglês:

Propolis is a complex mixture composed by salivary secretions of bees and a resinous and balsamic material collected by them from different part of plants. This material is well employed by people due its antimicrobial, antioxidant, anti-inflammatory, antiviral properties beside others. However, the chemical composition varies according the habitat and season. This work describes the identification of saturated hydrocarbons, methyl cinnamate, sitosterol cinnamate and ananixanthone isolated from the brown propolis produced in Bahia, Brazil, classified as Propolis Type 6. Besides, antioxidant activities and cytotoxicity of the extracts were evaluated by the DPPH quenching and Brine Shrimp Test. The extracts showed weak antioxidant activities and high cytotoxicity, especially the methanol and chloroformic extracts.

Resumo em Inglês:

Species of genus Sida are used around the world for a large amount of therapeutic treatments, including hyperglycemia. α-Glucosidase inhibitors are recognized as valuable tools for reducing postprandial hyperglycemia by retarding absorption of glucose. The effect of extracts and isolated compounds of S. acuta and S. rhombifolia on inhibition of α-glucosidase as primary screening of anti-hyperglycemic activity was tested using yeast and mammalian α-glucosidases. When yeast α-glucosidase was used the acetone extracts of S. acuta and S. rhombifolia showed IC50 values of 8.49 ± 0.66 and 8.10 ± 0.34 µg mL-1, respectively, and the most active compound was p-hydroxyphenethyl trans-ferulate (IC50 19.24 ± 1.73 µmol L-1) followed by β-sitosteryl glucopyranoside (IC5032.70 ± 1.35 µmol L-1). However, the activity of extracts and isolated compounds decreased significantly when mammalian α-glucosidase was used, indicating that substrates affinity is higher for type 1 enzymes. The antioxidant and anti-inflammatory activities of extracts and isolates were also tested since many diabetic complications are associated to the oxidative stress and inflammatory immune responses. Acetone extracts were the most active in all evaluations. p-Hydroxyphenethyl trans-ferulate, could be associated to these activities, since it was active in the three evaluations. This effect could be related to its phenolic character.

Resumo em Inglês:

Bismuth ferrite (BFO) and Ba-Nb-substituted BFO with compositions Bi1-xBaxFeO3 (x= 0, 0.10, 0.15 y 0.20), BiFe1-yNbyO3 (y= 0, 0.03, 0.06 y 0.09) y Bi1-xBaxFe1-yNbyO3 (x= 0.10 (y= 0, 0.03, 0.06 y 0.09) powders were synthesized using the citrate-gel method. Infrared spectroscopy indicated shifting of Bi/Ba-O and Fe/Nb-O bond vibrations and a structural transition was observed by X-ray diffraction. A Williamson-Hall (W-H) analysis revealed that Ba/Nb dopant reduces the particle size and increases the strain crystalline lattice. Impedance analysis suggests that electrical relaxation process is temperature dependent, for all compositions obtained. Furthermore, electrical conductivity increases with temperature showing a typical negative temperature coefficient of the resistance (NTCR) analogous to a semiconductor. Magnetization v magnetic field curves reveal weak ferromagnetic behaviour within the BiFeO3 doped with Ba and Nb, and co-doped with Ba-Nb, measured at room temperature.

Resumo em Inglês:

Volatile methylsiloxanes (VMS) are pollutants widely distributed in the environment due to its extensive uses and high volatility. The analysis of these compounds is commounly performed by gas chromatography - mass spectrometry (GC-MS), and it is dificult due to the presence of background contamination and volatile losses. Different preconcentration techniques such as purge and trap (P&T), headspace (HS) and headspace - solid phase microextraccion (HS-SPME) have been applied for the analysis of VMS in environmental samples. Alternatively, solvent extraction combined with large volume injection techniques has been an effective method for the analysis of complex matrices (eg. wastewater, sludges). In this review, the efficiency of the different methods reported for the analysis of VMS is discussed, and different solutions are proposed to minimize background contamination and volatilization.

Resumo em Inglês:

The photochemistry and photophysics of coordination compounds have been extensively investigated not only because their structure, stability, reactivity dependence on the metal center oxidation state and the coordinated ligand; but also for their electronic transitions in a wide range of visible radiation. The knowledge of light absorption, excited state deactivation, sensitization and quenching processes are crucial to their manipulation aiming the development of systems capable of execute useful functions such as photosensors and/or probes, luminescent devices and molecular systems to convert sunlight into other types of energy. In this review, the progresses and challenges of biomolecules photosensors, organic light emitting diodes and CO2 photoreduction catalysts based on ruthenium(II), rhenium(I) or iridium(III) coordination compounds are discussed based on their photochemical and photophysical processes.

Resumo em Inglês:

As the result of research work and teaching, the Instituto de Química da Universidade de São Paulo generates 10,000L/year of used solvent mixtures. Although recovery is usually considered an attractive alternative to incineration, a fundamental question remained unanswered: how to ascertain and compare environmental impacts of distillation of a waste mixture of solvents or its disposal by incineration. To this end, after separation of the components of ten solvent mixtures by distillation, Ecosolvent® software was used to compare, for both alternative methods, the EI99 values for some parameters like mass balance, energy and water consumption, gaseous emissions and transportation to the incinerating facility. Results showed that for nine of such mixtures the EI99 parameters were lower for distillation than for incineration.

Resumo em Inglês:

This paper comprises a case study within the scope of Chemistry teacher training that aimed to analyze the process of professional development progression of a future teacher. Therefore, we sought to identify the didactic models present in the Work Plans developed in primary schools by graduate students during supervised training. To do so, Rafael Porlán Ariza and Ana Garcia Rivero's theoretical foundation about the knowledge evolution of the teacher's professional knowledge was employed. The investigation results made evident that, during the internship period, the teacher progressed to stages deemed to be desirable to the professional development process. Moreover, evidence was found of the relation between the different academic course experiences and the teaching practices employed by the future teacher. Thus, contributions are pointed out for the comprehension about the path of professional development progression of teachers under training.

Resumo em Inglês:

Understanding instrumental analysis is essential for obtaining reliable analytical results required by chemists in a variety of research areas and industrial activities. All instrumental techniques involve undesirable background (BG) signals originated either from concomitants in the sample or by spurious (e.g. electrical or optical) effects intrinsically related to the measurement process. BG signals may affect accuracy, precision and detection limits. Techniques characterized by low BG stands out by high detectability even when they are based on processes with low efficiency (e.g. low quantum yields and low efficiency of thermal excitation). However, minor attention has been given to this topic in analytical chemistry courses hindering students' understanding of the BG concept and its impact on the analytical performance. Although in some analytical techniques BG is well-defined and successfully compensated, some of them still need further elucidation. Sources of BG and strategies for its minimization and correction are didactically discussed for a variety of analytical techniques, including molecular and atomic spectrometry, electroanalytical methods, and separation techniques. Historical aspects and recent approaches are also addressed.

Resumo em Inglês:

Herein, we propose an interdisciplinary experiment for undergraduate course that involves concepts of organic and physical chemistry. Firstly, we propose the synthesis of three nitrophenyl acetates, varying the substituent position. Afterwards, we describe the construction of a homemade colorimeter using inexpensive materials and LED as both emission and detection dispositives. Finally, the colorimeter is used to follow the nucleophilic acyl transfer reactions catalyzed by imidazole under pseudo-first order conditions for the reactions of p-nitrophenyl, o-nitrophenyl and m-nitrophenyl acetate with imidazole. The substituent effect is correlated to the reactivity of the acetates, one of the benchmarks of a physical organic chemical approach. The effect of imidazole concentration is also evaluated. The proposed experiment is interesting because the students can thoroughly understand how a spectrophotometer works and since each student can construct their own colorimeter, they don't have to rely on any equipment infrastructure. Additionally they can correlate two important areas: organic and physical chemistry by using a kinetic study in the understanding of organic reactions. Indeed, physical organic chemistry is a field of increasing interest specially for elucidating mechanisms and introducing students to this interdisciplinary approach is interesting since several undergraduate concepts are covered.