Showing papers in "Química Nova in 2019"

Design of immobilized enzyme biocatalysts: drawbacks and opportunities

Abstract: The enzymatic processes are increasingly highlights, especially in the synthesis of chemical products with high added value. The enzyme immobilization can improve industrial biocatalytic processes. The immobilization of enzymes provides the production of efficient, stable biocatalysts, possibility of reuse and easy purification of the products, when compared to the free enzymes. There is a growing research for more efficient methods of enzyme immobilization. In this context, the choice of support and immobilization strategy can significantly improve the final enzymatic properties. In this review paper, we aimed to discuss the versatility of biocatalysts immobilized enzymes design, focusing on the opportunities and disadvantages for each method presented. They discussed the recent development of enzyme immobilization methods and applications relating the final properties of the produced biocatalysts with the desired goals.

Development of an automated method to perform a quantitative study of particle size distribution and the effect of a conductive layer in scanning electron microscopy

Abstract: The determination of particle size distribution is an important parameter for controlling industrial processes, particularly in the field of pharmaceuticals. It is also an important parameter for characterizing nanoparticles. The best technique for determining particle size distribution is scanning electron microscopy. The process of counting particles is typically performed manually, which requires both more time and a higher standard deviation than automatic methods. This study shows the results of a particle counting procedure that relies on a fully automated method that was found to improve the reproducibility of the measurement. The effect on the diameter of near-spherical polymer nanospheres between 20 and 100 nm (mean of 60 nm) when samples were coated by a conducting layer (such as gold or carbon) was also evaluated. The images were collected using a field emission scanning electron microscope and then processed using the ImageJ program. Results showed that the method proposed in this work produces mean diameter values in accordance with NIST-traceable near-spherical polymer nanospheres for the sample without coating. The study also revealed two main effects of the conductive coating: changes to topography and an increase in mean particle diameter.

Spectroscopic characterization of pedot:pss conducting polymer by resonance raman and serrs spectroscopies

Abstract: Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) synthesis was monitored by resonance Raman (RR) and surface-enhanced resonance Raman scattering (SERRS) spectroscopies and both the oxidation of the polymer and the effects of chain length were assessed by vibrational analysis. It was supported by theoretical models of oligomers, with charge ranging from 0 to +6 and size varying from 2 to 16 3,4-ethylenedioxythiophene (EDOT) repeat units, described through density functional theory. The symmetric CαCβ stretching band observed at ca. 1426 cm shifts to higher wavenumbers for reaction times varying from 2 to 9 hours and stabilizes at intermediate wavenumbers for longer times. The former behavior was ascribed to the increase of concentration of oxidized species, which was corroborated by calculated wavenumbers for oligomer models when their charges changed from neutral to +6. The behavior observed for longer reaction times was associated with the growth of chains. It was also observed through SERRS spectroscopy that small chains of the polymer, obtained in the early time of the synthesis, adsorbs on gold nanoparticle surfaces through interactions via oxidized residues. In this way, RR and SERRS spectroscopies were valuable tools to follow the synthetic procedures of PEDOT:PSS, allowing the determination of the structural evolution of the polymer.

Identification of aroma-active volatile compounds in Pouteria sapota fruit by aroma extraction dilution analyses (AEDA)

Abstract: Pouteria sapota is a tropical fruit that is commonly found in central and north part of South America where is widely consumed by its biofunctional properties. The aroma active volatile compounds of Pouteria sapota fruit were studied by using the molecular sensory approach, which includes a SAFE (Solvent Assisted Flavor Evaporation) distillation to get a volatile extract that resembles the fruit aroma, and the combination of GC-O (Gas Chromatography coupled to Olfactometry) with GC-MS analyses to identify odour-active compounds. By AEDA (Aroma Extract Dilution Analysis), β-damascenone, furaneol, linalool, (Z)-3-hexenal, and benzaldehyde, were identified as key aroma compounds in this fruit.

Hybrid atomic orbitals in organic chemistry. part 2: critique of practical aspects

Abstract: The importance of hybrid atomic orbitals, in both general and organic chemistry, is reviewed. Every contemporary textbook of organic chemistry introduces the directed-valence (e.g. sp3, sp2, sp) model, but the suitability of these hybrid orbitals for use in the teaching of molecular structure has been increasingly questioned. Based on a critical survey of the literature, we submit seven practical criteria that deprecate the use of hybrid orbitals in a pedagogical context. We suggest how the teaching of organic chemistry without hybrid orbitals will provide students with an enhanced education.

Preparation and characterization of a quercetin-tetraethyl ether-based photoprotective nanoemulsion

Abstract: Although Quercetin absorbs in the UVA/UVB electromagnetic region, it is limited for applications as a UV filter due to its low lipophilicity and capacity to penetrate the epidermis. In order to overcome this limitation, we synthetized and evaluated the photo protective properties of a derivative obtained from Quercetin. The derivative was prepared by alkylation of Quercetin with iodoethane and characterized by IR and NMR spectroscopy. The in vitro Solar Protection Factor was determined by the Mansur method and the cytotoxicity was evaluated using hepatocellular cell (Hep G2) cells. Finally, Quercetin and the corresponding derivative were incorporated in nanoemulsions. Nanoemulsions with particles sizes between 53 and 73 nm were obtained, and polydispersity indexes were around 0.1, indicating good homogeneity of the nanoemulsion particles. The cell viability study for the Quercetin derivative indicated a very low cytotoxicity profile. The chemical modification of Quercetin resulted in a promising compound with improved properties desirable for skin penetration and incorporation into sunscreen formulations.

Chemometric tools and ftir-atr spectroscopy applied in milk adulterated with cheese whey

Abstract: Brazilian law forbids the addition of cheese whey in milk. However, adulteration with cheese whey is one of the most applied fraud due to its low cost. The detection of this fraud is the quantification of Caseinomacropeptide (CMP). The CMP is a constituent of the whey that can be used as adulteration marker. Thus, an analytical method capable of identifying CMP by Fourier Transform Infrared Spectra (FTIR) was developed using chemometrics methods. Firstly, we attempted to develop an exploratory analysis model by Hierarchical Grouping Analysis (HCA) and Principal Component Analysis (PCA) that indicated similarity between samples of raw milk and semi-skimmed milk. Moreover, in the PCA scores, it was possible to observe a tendency of separation between samples with different concentrations of CMP. Afterwards, multivariate regression models were used for Partial Least Squares (PLS), Partial Least Square with Interval Synergism (siPLS) and Supporting Machines with Least Squares (LS-SVM) to quantify the adulteration in different types of milk by Cheese serum through the CMP. All the models were then compared to each other and the results of the official method with Liquid Chromatography Tandem mass spectrometry (LCMS/MS) analysis used by the Ministry of Livestock and Supply (MAPA). The model LS-SVM, employing the full spectrum, obtained the best result compared to the other models (PLS and siPLS) to quantify the CMP in the milk samples.

Npk: essentials for sustainability

Abstract: Human population growth and development has been largely dependent on non-renewable natural resources, which cannot be indefinitely sustained. Beyond, coal and other abundant resources cannot continue to be used at current rates due to their impact on the environment and climate. It is thus important to replace as much as possible the fossil fuels and scarce minerals as sources of energy and industrial raw materials. Biomass plays a key role in this scenario, since its availability depends on abundant but often misused resources: air, water, sunlight and land. The “oil shocks”, the recognition of impending resource shortages, the global pollution and climate change led many governments and organizations to create roadmaps to Bioeconomy. This includes the growing use of plants and animals to produce energy and raw materials, but it cannot create food scarcity. Agriculture depends on the plant macronutrients N, P and K, and this article discusses their role in plant and animal growth, production and consumption, dependence on non-renewable minerals and energy and perspectives for increasing their efficiency. Special attention is given to Brazilian agriculture that is heavily dependent on imported NPK, requiring strategic action and research.

Impactos da mudança de vegetação local no aporte de matéria orgânica para um estuário tropical preservado (Estuário do Rio Itapicuru – BA)

Abstract: Lucas M. Guimarãesa, Tiago de Abreu C. Limaa, Elvis Joacir De Françab, Gilberto N. de Arrudab, José Roberto B. de Souzac e Ana Cecília R. de Albergaria-Barbosaa,*, Departamento de Oceanografia, Instituto de Geociências, Universidade Federal da Bahia, 40170-115 Salvador – BA, Brasil Centro Regional de Ciências Nucleares do Nordeste, Comissão Nacional de Energia Nuclear, 50740-545 Recife – PE, Brasil Departamento de Física da Terra e Meio Ambiente, Instituto de Física, Universidade Federal da Bahia, 40170-115 Salvador – BA, Brasil

Evaluation of cocaine samples seized in the streets of the state of rio de janeiro, brazil

Abstract: Fifty-two samples of street cocaine seized in the state of Rio de Janeiro, from May 2016 to April 2017, were evaluated according to their purity, presence of inorganic and sugar diluents and concentration of pharmacologically active adulterants. Cocaine contents, as well as the adulterants caffeine, lidocaine and phenacetin, were evaluated by gas chromatography coupled with mass spectrometry. The samples were screened by Raman spectroscopy for the presence of inorganic diluents and carbohydrates. The main diluents were calcium carbonate and sodium bicarbonate, which were found in 93% and 71% of the cocaine hydrochloride samples, respectively. Caffeine was found in 91% of the cocaine hydrochloride samples, while phenacetin was found in all freebase cocaine samples. Freebase cocaine samples were majorly composed of pharmacological active compounds (adulterants), unlike cocaine hydrochloride samples, which were majorly composed of inorganic compounds (diluents). It could be observed, by Raman Spectroscopy associated to multivariate analysis, similarities on cocaine hydrochloride composition according to certain criminal gangs. The percentage of pharmacological active compounds varied significantly on the analyzed samples, showing that these adulterants are indiscriminately added to street cocaine, what may increase consumers’ health risks.

Cuprous oxide nanoparticles: preparation and evaluation of antifouling activity

Abstract: There are few methods to obtain uniform and well dispersed cuprous oxide nanoparticles, which limits its application widely. In this research, an improved method to prepare nanoparticles was introduced. Cuprous oxides were prepared by the reduction of cupric nitrate, with hydrazine hydrate as a reductant in the presence of glucose. The nanoparticles formed have the characteristics of small particle size and uniform distribution. The crystalline structure and morphological characteristics were analyzed by XRD and TEM respectively. The result showed they were pure sphere polycrystal. The particle size is about 9nm. Subsequently, the antifouling activity was tested in detail through comparative experiments. The results indicated that the effective concentration of nanoparticles was obviously lower than ordinary cuprous oxide.

Study of the chromium(vi) removal from aqueous systems by cobalt nanoparticles

Abstract: The cobalt nanoparticles (NPs-Co) were synthesized and applied in the removal of Cr(VI). The obtained nanomaterials presented magnetic properties and were characterized by the techniques of Transmission Electron Microscopy and X-ray diffraction. The NPs-Co, with a diameter of less than 50 nm, had a composition based on metallic cobalt and cobalt oxide. The NPs-Co were applied in the removal of Cr(VI) being evaluated different parameters such as time of equilibrium, initial pH, dose of NPs-Co, concentration of Cr(VI), and system temperature. The removal of Cr(VI) was favored at lower pH values, being about 100% at pH 2.0. With the increase of Cr(VI) concentration from 40.0 to 300.0 mg L the removal decreased from 80 to 15%. The NPs-Co dose promoted an increase in removal reaching 90% at a dose of 1.0 g L. The removal process was spontaneous and endothermic, and the Langmuir isotherm model fit better to experimental data. The maximum removal capacity was approximately 70.0 mg g. The removal kinetics followed the pseudo-second order model. The mechanism of Cr(VI) removal occurred through adsorption by electrostatic interactions between CrO4 anion and Co-NPs, followed by reduction of Cr(VI) to Cr(III) and, lastly, co-precipitation of Cr(III) as Cr(OH)3 on the NPs-Co.

Endophytic fungi from the brazilian flora and their employment in biotransformation reactions

Abstract: The biotransformation reactions are used as a successful alternative to derivatization by the traditional chemistry because they conduct to uncommon reactions, which would hardly be carried out by chemical synthesis. A wide diversity of compounds may be metabolized by fungi, leading to chemical derivatives through selective reactions that work under ecofriendly conditions. Endophytic fungi live in symbiosis with health tissues of plants. The employment of endophytic fungi as enzymatic sources to biotransformation reactions is very promising since these microorganisms came from uncommon and underexplored habitat. The environmental conditions directly influence the composition of the endophytic microbiota and its genetic expression, which could change also the production of the enzymes. The extraordinary richness of the Brazilian biodiversity is a key factor in the diversification of the endophytic community. The present review presents a mapping of the biotransformation reactions catalyzed by Brazilian endophytic fungi. Our findings contribute both to the appreciation of these fungi in the chemical derivatization and for the preservation of the Brazilian species.

PHYTOTOXIC CONSTITUENTS FROM ENDOPHYTIC FUNGUS Xylaria cubensis ASSOCIATED WITH Eugenia brasiliensis

Abstract: Carolina R. Biasettoa, Andressa Somensia, Viviane de C. P. Abdallab, Lucas M. de Abreuc, Sonia C. J. Gualtierib, Ludwig H. Pfenningd, Vanderlan da S. Bolzania and Angela R. Araujoa,*, Departamento de Química Orgânica, Instituto de Química, Universidade Estadual Paulista, 14800-900 Araraquara – SP, Brasil Departamento de Botânica, Universidade Federal de São Carlos, 13565-905 São Carlos – SP, Brasil Departamento de Fitopatologia, Universidade Federal de Viçosa, 36570-000 Viçosa – MG, Brasil Departamento de Fitopatologia, Universidade Federal de Lavras, 37200-000 Lavras – MG, Brasil

Raman studies of bis(phenylterpyrazine)iron(ii) and supramolecular species with pentacyanidoferrate(ii) ions

Abstract: The chemistry and spectroscopy of the iron(II) phenylterpyrazine complex, [Fe(phtpz)2]2+, were investigated in comparison with the analogous phenylterpyridine species, Fe(phtpy)2]2+, and the results indicated a strong electronic delocalization on the Fe(II) terimine chromophore encompassing the lateral pyrazyl groups. The delocalized nature of the molecular orbitals involved in the electronic excitation precluded a direct assignment of the pyridine and pyrazine vibrations in the complex. However, the capability of the terpyrazine complex to bind transition metal ions, such as the [Fe(CN)5]3- species, allowed to generate pentanuclear complexes displaying characteristic charge-transfer and resonance Raman spectra, revealing the pyrazine vibrations in the complex. The [Fe(CN)5]3- containing species also yielded polymeric compounds in presence of transition metal ions, exhibiting intervalence transfer bands and chemical similarities with the Prussian Blue complex.

Determinação de designer drugs em saliva por paper spray mass spectrometry

Abstract: DETERMINATION OF DESIGNER DRUGS IN SALIVA BY PAPER SPRAY MASS SPECTROMETRY. Determination of two drugs of abuse in saliva has been performed by Paper Spray Ionization Mass Spectrometry (PSI-MS) using a Molecularly Imprinted Polymer (MIP) coated paper as substrate. The method has been optimized for quantification of 3,4-methylenedioxyN-methylamphetamine (MDMA) and methamphetamine, 3,4-methylenedioxyamphetamine (MDA) from synthetic saliva samples. Rapid analysis (~ 1 min) of designer drugs in saliva is demonstrated using MIP-PSI-MS. Both precursor ions of MDMA and MDA were confirmed by tandem mass spectrometry (MS/MS) experiments by elucidating the fragmentation patterns formed via collisioninduced dissociation (CID). The MIP-PSI-MS method showed greater selectivity for MDMA and MDA in comparison with other analytes. Signal intensity ratios of the most important transitions for MDMA (194 → 163) and MDA (180 → 163) were found linear (R > 0,99) in the range 25-500 μg L. The LOD and LOQ for MDMA were 1.11 μg L and 18.73 μg L, respectively, and for MDA were 3.42 μg L and 21.66 μg L, respectively. The precision and accuracy values were determined below 4%, and the recoveries about 100%, without pre-concentration/enrichment or separation steps. The MIP-PSI-MS method displays the potential for rapid screening for selective quantitative determination of illicit drugs in saliva samples.

Binary co-culture selection from marine-derived microorganisms for differential production of specialized metabolites

Abstract: Nowadays the discovery of new compounds from microorganisms has substantially decreased. Genomic studies have shown that certain genes are not expressed under standard laboratory conditions. In order to overcome this problem, several methods including microorganism co-culture have been developed. The aim of this work was to select binary co-cultures of marine-derived microorganisms to pursue further chemical studies. From 15 microorganisms, 151 interactions assays in solid media were performed using two different methodologies: distance assays and contact assays that allowed to distinguish between interactions due to diffusible compounds or due to cell-cell contact. For distance assays, the metabolic production changes were evaluated using 3 zones: two corresponding to each microorganism colony, and a third zone corresponding to the interaction zone. This division zone strategy allowed to assess the diffusion compounds gradient, and to suggest the producer microorganism of the induced compounds. The metabolic production of the co-cultures was evaluated using HPLC-DAD and NMR. Seven co-cultures were identified to be able to induce changes in the metabolic production. Remarkably, the co-culture between the fungus Purpureocillium sp. PNM-67 and the bacteria Rhodococcus sp. RKHC-26 or Gordonia sp. PNM-25 induce production of a red dye in the fungus. These are the first successful examples of interaction between a fungus and a mycolic acid-containing bacteria.

Desenvolvimento de metodologia de revelação de impressão digital latente com chalconas

Abstract: DEVELOPMENT OF METHODOLOGY OF LATENT FINGERPRINT REVELATION WITH CHALCONES. Fingerprints are unique for each individual contributing to human identification in forensic cases. Visualization of latent fingerprints usually involves the use of a chemical substance that creates a contrast between fingerprint residues and the surface on which the print was deposited. Commercial powders used as fingerprint developers by papilloscopy have relatively high costs due to their importation and chemical composition. (E-1,3-diphenylprop-2-en-1-one, E-1-phenyl-3-(4-methylphenyl))prop-2-en-1-one but only one compound was highlighted, E-3-(3-nitrophenyl)-1-phenylprop-2-em-1-one). The composite was selected for its suitable properties (adhesion and texture) of visualization of the digital, providing the obtaining of clear revelations with identification of minutiae and singular points of the fingerprints. Identification, magnetic resonance, granulometry and contact surface evaluation with chalcones such as sebaceous and natural deposition with development in different materials such as plastic, metal and glass were applied for the application of fingerprint development. The compound was tested in eight volunteers regardless of gender and age, presenting satisfactory results for fingerprint development on glass and metal surfaces.

Biorremediação de efluentes por meio da aplicação de microalgas - uma revisão

Abstract: BIORREMEDIATION OF INDUSTRIAL EFFLUENT USING MICROALGAE. National industrial effluent remediation strategies are largely outdated, which makes these processes costly and at the same time inefficient. Among the most worrying compounds are heavy metals, which have bioaccumulative and toxic characteristics to living beings. In addition to these, high nutrient loads constitute a huge environmental problem, since the devastation promoted by eutrophic niches is capable of disrupting complex food chains. This paper presents a bibliographical review of the current researches that are applying biomass from microalgae in effluent bioremediation, both domestic and industrial (mainly the latter, since its pollution potential is abruptly greater). Such strategy is interesting since the diversity of these microorganisms is abundant, propitiating the application of them in various conditions. Another point to be taken into consideration is the fact that many species of microalgae produce large amounts of lipids, many of which have potential application in the production of biodiesel.

Analysis of the chemical reactivity of indaziflam herbicide and its metabolites through global and local reactivity descriptors

Abstract: In the present work, the chemical reactivity of indaziflam N-[(1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1 yl]-6-[(1R)-1-16 fluoroethyl]-1,3,5-triazine-2,4-diamine so called indaziflam (IND) and its metabolites: triazine indanone (ITI), indaziflam carboxylic acid (ICA) and fluoroethyldiaminotriazine (FDAT) was analyzed. The calculations were performed at the X/6 311++G(2d,2p) (where X=B3LYP, M06, M06L and wB97XD) level of theory, in the aqueous phase. The results indicate that ITI is the more reactive followed by ICA, IND and FDAT. The distribution of the active sites was determined evaluating the Fukui function employing the frozen core and finite difference approximations. For electrophilic attacks, IND shows the more reactive zone on the benzene ring, ITI and ICA on the nitrogen atom in the central section and FDAT on its nitrogen atoms. The more nucleophilic sites for IND are observed on the carbon atoms of triazine, on the carbonyl group for ITI, on the carboxylic group for ICA, and on the nitrogen atoms of triazine for FDAT. For free radical attacks case, the more reactive sites for IND are on the benzene and triazine rings, on the carbonyl group, nitrogen of the central section, and nitrogen atoms of triazine, for ITI, carboxylic group for ICA, and on the nitrogen atoms of triazine ring for FDAT.