The Effect of Goethites on the Polymerization of Glycine and Alanine Under Prebiotic Chemistry Conditions.

After pre concentration of monomers, polymerization is the second most important step for molecular evolution. The formation of peptides is an important issue for prebiotic chemistry and consequently for the origin of life. In this work, goethite was synthesized by two different routes, named goethite-I and goethite-II. Although both samples are goethite, Far-FT-IR spectroscopy and EPR spectroscopy showed differences between them, and these differences had an effect on the polymerization of glycine and alanine. For the amino acid polymerization, three protocols were used, that resembled prebiotic Earth conditions: a) amino acid plus goethite were mixed and heated at 90 °C for 10 days in solid state, b) a wet impregnation of the amino acid in the goethite, with subsequent heating at 90 °C for 10 days in solid state, and c) 10 wet/dry cycles each one for 24 h at 90 °C. Experiments with glycine plus goethite-II, using protocols B and C, produced only Gly-Gly. In addition, for the C protocol the amount of Gly-Gly synthesized was 3 times higher than the amount of Ala-Ala. Goethite-I presented a decrease in the EPR signal, when it was submitted to the protocols with and without amino acids. It is probable the decrease in the intensity of the EPR signal was due to a decrease in the imperfections of the mineral. For all protocols the mixture of alanine plus goethite-I or goethite-II produced c(Ala-Ala). However, for wet/dry cycles, protocol C presented higher yields (p < 0.05). In addition, Ala-Ala was produced using protocols A and C. The c(Ala-Ala) formation fitted a zero-order kinetic equation model. The surface areas of goethite-I and goethite-II were 35 m2 g-1 and 37 m2 g-1, respectively. Thermal analysis indicated that the mineral changes the thermal behavior of the amino acids. The main reactions for the thermal decomposition of glycine were deamination and dehydration and for alanine was deamination.

Influence of Spray-Drying and Room Temperature Storage on the Anti- and Prooxidant Properties of Fermented Juçara Pulp.

Many fruits and vegetables contain compounds with antioxidant properties, but the processing and storage conditions of the food industry may damage these beneficial compounds and produce free radicals that are associated with oxidative stress. This study aims to evaluate in vitro the antioxidant capacity and prooxidant effects of juçara pulp fermented with Lactobacillus reuteri or Lactobacillus plantarum before and after spray-drying with maltodextrin, gum arabic or gelatin and stored at 25 °C for 90 days. The antioxidant capacity was assessed by measuring the ability to scavenge reactive oxygen species (ROS) in the neutrophil respiratory burst and free radical 2,2-diphenyl-1-picryl-hydrazyl (DPPH), and by determining the total phenolic content. The prooxidant effects were analyzed as free radical formation measured by electronic paramagnetic resonance (EPR). Fermentation by both bacteria increased the antioxidant activity, while the spray-drying process decreased the content of phenolic compounds (65-85%) and the DPPH scavenging ability, depending on the carrier usage. All of the samples inhibited ROS in the neutrophil burst, and the juçara pulp fermented by L. reuteri and dried with gum arabic exhibited the best performance. Spray-drying did not influence the intensity or type of free radicals detected by EPR. However, storage at room temperature decreased the antioxidant capacity and increased free radical formation.

The effect of pH and ionic strength on the adsorption of glyphosate onto ferrihydrite.

Although, glyphosate (N-(phosphonomethyl) glycine) is one of the most widely used herbicides in the world, its interaction with poorly crystalline iron oxides, such as ferrihydrite, is not well studied. In this research, we examined the adsorption of glyphosate onto ferrihydrite using infrared spectroscopy (FT-IR), electron paramagnetic resonance spectroscopy (EPR), adsorption kinetic models and adsorption isotherm models. The effect of pH and sodium chloride concentration on the adsorption of glyphosate onto ferrihydrite as well as the effect of extractors (CaCl2 0.010 mol L-1 and Mehlich) on the desorption of glyphosate were also evaluated. There are two important findings described in this work. First, 84% of adsorbed glyphosate strongly interacted to ferrihydrite as an inner-sphere complex and phosphate and amine groups are involved in this interaction. Second, an increase of sodium chloride salt concentration increased the adsorption of glyphosate onto ferrihydrite. The non-linear Langmuir model and pseudo second order model showed a good agreement of theoretical limit of glyphosate adsorbed onto ferrihydrite, 54.88 µg mg-1 and 48.8 µg mg-1, respectively. The adsorption of glyphosate onto ferrihydrite decreased when the pH increased. Under the conditions used in this work, EPR spectra did not show dissolution of ferrihydrite. Surface area, pore volume and pHpzc of ferrihydrite decreased after adsorption of glyphosate.

Optimization of ultrasound-assisted extraction of grape-seed oil to enhance process yield and minimize free radical formation.

BACKGROUND: Grape seeds are a relatively abundant source of oil and bioactive compounds. To use this byproduct, the current work aimed to optimize the ultrasound-assisted extraction (UAE) of grape-seed oil to obtain greater process yield and minimize free radical formation in the oil. RESULTS: The optimal condition was 15 °C with an ultrasonic wave amplitude of 42 µm, leading to a process yield of 82.9% and content of free radicals of 14.7 × 1017 kg-1 and 3.4 × 1018 kg-1 for samples stored for 7 and 30 days, respectively. No significant differences in fatty acid composition and acidity and iodine values were observed between samples. The oil obtained by ultrasound had greater phenolic compound content and antioxidant activity by ferric reduction than the control sample (without ultrasound application). However, higher content of free radicals and peroxide value was observed. CONCLUSION: Sonication improved extraction yield when compared to the process without ultrasound application. Moreover, UAE favored the extraction of phenolic compounds. As it enhanced process yield with the minimum formation of free radicals, UAE is a promising oil-extraction technology. © 2018 Society of Chemical Industry.

ESR and calculations on electronic structure of phenalenyl and phenalenyl derivative radicals.

Calculations on electronic structure of the perinaphthenyl radical and phenalenyl derivative radicals responsible for the composition of the ESR spectrum of marine diesel under heating were performed to obtain support for the experimental ESR results. The parameters calculated were the hyperfine coupling constants (A), which were then used for comparison with the experimental data. The energy-minimized structures were obtained using the density functional theory method. In all cases, the symmetry system was taken into account in theoretical calculations. The differences between experimental and theoretical values were below 7% for nearest hydrogens in molecules, named hyperfine coupling constant A (first neighbors) and 18% for farthest hydrogens atoms named hyperfine coupling constants A' (second neighbors), for all structures analyzed.

Adsorption of adenine and thymine on zeolites: FT-IR and EPR spectroscopy and X-ray diffractometry and SEM studies.

The interactions of adenine and thymine with and adsorption on zeolites were studied using different techniques. There were two main findings. First, as shown by X-ray diffractometry, thymine increased the decomposition of the zeolites (Y, ZSM-5) while adenine prevented it. Second, zeolite Y adsorbed almost the same amount of adenine and thymine, thus both nucleic acid bases could be protected from hydrolysis and UV radiation and could be available for molecular evolution. The X-ray diffractometry and SEM showed that artificial seawater almost dissolved zeolite A. The adsorption of adenine on ZSM-5 zeolite was higher than that of thymine (Student-Newman-Keuls test-SNK p<0.05). Adenine was also more greatly adsorbed on ZSM-5 zeolite, when compared to other zeolites (SNK p<0.05). However the adsorption of thymine on different zeolites was not statistically different (SNK p>0.05). The adsorption of adenine and thymine on zeolites did not depend on pore size or Si/Al ratio and it was not explained only by electrostatic forces; rather van der Waals interactions should also be considered.

Adsorption of cysteine on hematite, magnetite and ferrihydrite: FT-IR, Mössbauer, EPR spectroscopy and X-ray diffractometry studies.

In the present paper, the adsorption of cysteine on hematite, magnetite and ferrihydrite was studied using FT-IR, electron paramagnetic resonance (EPR), Mössbauer spectroscopy and X-ray diffractometry. Cysteine was dissolved in artificial seawater (two different pHs) which contains the major constituents. There were two main findings described in this paper. First, after the cysteine adsorption, the FT-IR spectroscopy and X-ray diffractometry data showed the formation of cystine. Second, the Mössbauer spectroscopy did not show any increase in the amount of Fe(2+) as expected due the oxidation of cysteine to cystine. An explanation could be that Fe(2+) was oxidized by the oxygen present in the seawater or there occurred a reduction of cystine by Fe(2+) generating cysteine and Fe(3+). The specific surface area and pH at point of zero charge of the iron oxides were influenced by adsorption of cysteine. When compared to other iron oxides, ferrihydrite adsorbed significantly (p < 0.05) more cysteine. The pH has a significant (p < 0.05) effect only on cysteine adsorption on hematite. The FT-IR spectroscopy results showed that cystine remains adsorbed on the surface of the iron oxides even after being mixed with KCl and the amine and carboxylic groups are involved in this interaction. X-ray diffractometry showed no changes on iron oxides mineralogy and the following precipitated substances were found along with the iron oxides after drying the samples: cysteine, cystine and seawater salts. The EPR spectroscopy showed that cysteine interacts with iron oxides, changing the relative amounts of iron oxides and hydroxide.

Adsorption of adenine, cytosine, thymine, and uracil on sulfide-modified montmorillonite: FT-IR, Mössbauer and EPR spectroscopy and X-ray diffractometry studies.

In the present work the interactions of nucleic acid bases with and adsorption on clays were studied at two pHs (2.00, 7.00) using different techniques. As shown by Mössbauer and EPR spectroscopies and X-ray diffractometry, the most important finding of this work is that nucleic acid bases penetrate into the interlayer of the clays and oxidize Fe(2+) to Fe(3+), thus, this interaction cannot be regarded as a simple physical adsorption. For the two pHs the order of the adsorption of nucleic acid bases on the clays was: adenine ≈ cytosine > thymine > uracil. The adsorption of adenine and cytosine on clays increased with decreasing of the pH. For unaltered montmorillonite this result could be explained by electrostatic forces between adenine/cytosine positively charged and clay negatively charged. However for montmorillonite modified with Na(2)S, probably van der Waals forces also play an important role since both adenine/cytosine and clay were positively charged. FT-IR spectra showed that the interaction between nucleic acid bases and clays was through NH(+) or NH (2) (+) groups. X-ray diffractograms showed that nucleic acid bases adsorbed on clays were distributed into the interlayer surface, edge sites and external surface functional groups (aluminol, silanol) EPR spectra showed that the intensity of the line g ≈ 2 increased probably because the oxidation of Fe(2+) to Fe(3+) by nucleic acid bases and intensity of the line g = 4.1 increased due to the interaction of Fe(3+) with nucleic acid bases. Mössbauer spectra showed a large decreased on the Fe(2+) doublet area of the clays due to the reaction of nucleic acid bases with Fe(2+).

Biodegradation of bio-sourced and synthetic organic electronic materials towards green organic electronics.

Ubiquitous use of electronic devices has led to an unprecedented increase in related waste as well as the worldwide depletion of reserves of key chemical elements required in their manufacturing. The use of biodegradable and abundant organic (carbon-based) electronic materials can contribute to alleviate the environmental impact of the electronic industry. The pigment eumelanin is a bio-sourced candidate for environmentally benign (green) organic electronics. The biodegradation of eumelanin extracted from cuttlefish ink is studied both at 25 °C (mesophilic conditions) and 58 °C (thermophilic conditions) following ASTM D5338 and comparatively evaluated with the biodegradation of two synthetic organic electronic materials, namely copper (II) phthalocyanine (Cu-Pc) and polyphenylene sulfide (PPS). Eumelanin biodegradation reaches 4.1% (25 °C) in 97 days and 37% (58 °C) in 98 days, and residual material is found to be without phytotoxic effects. The two synthetic materials, Cu-Pc and PPS, do not biodegrade; Cu-Pc brings about the inhibition of microbial respiration in the compost. PPS appears to be potentially phytotoxic. Finally, some considerations regarding the biodegradation test as well as the disambiguation of "biodegradability" and "bioresorbability" are highlighted.

Cysteine, thiourea and thiocyanate interactions with clays: FT-IR, Mössbauer and EPR spectroscopy and X-ray diffractometry studies.

The present study examined the adsorption of cysteine, thiourea and thiocyanate on bentonite and montmorillonite at two different pHs (3.00, 8.00). The conditions used here are closer to those of prebiotic earth. As shown by FT-IR, Mössbauer and EPR spectroscopy and X-ray diffractometry, the most important finding of this work is that cysteine and thiourea penetrate into the interlayer of the clays and reduce Fe(3+) to Fe(2+), and as consequence, cystine and c,c'-dithiodiformamidinium ion are formed. This mechanism resembles that which occurs with aconitase. This is a very important result for prebiotic chemistry; we should think about clays not just sink of molecules, but as primitive vessels of production of biomolecules. At pH 8.00, an increasing expansion was observed in the following order for both minerals: thiourea > thiocyanate > cysteine. At pH 3.00, the same order was not observed and thiourea had an opposite behavior, being the compound producing the lowest expansion. Mössbauer spectroscopy showed that at pH 8.00, the proportion of Fe(2+) ions in bentonite increased, doubling for thiourea, or more than doubling for cysteine, in both clays. However, at pH 3.00, cysteine and thiourea did not change significantly the relative amount of Fe(2+) and Fe(3+) ions, when compared to clays without adsorption. For thiocyanate, the amount of Fe(2+) produced was independent of the pH or clay used, probably because the interlayers of clays are very acidic and HSCN formed does not reduce Fe(3+) to Fe(2+). For the interaction of thiocyanate with the clays, it was not possible to identify any potential compound formed. For the samples of bentonite and montmorillonite at pH 8.00 with cysteine, EPR spectroscopy showed that intensity of the lines due to Fe(3+) decreased because the reaction of Fe(3+)/cysteine. Intensity of EPR lines did not change when the samples of bentonite at pH 3.00 with and without cysteine were compared. These results are in accordance with those obtained using Mössbauer and FT-IR spectroscopy.

On the antioxidant activity of eumelanin biopigments: a quantitative comparison between free radical scavenging and redox properties.

The antioxidant activity of eumelanin, a ubiquitous pigment in flora and fauna, constitutes one of its most fascinating physicochemical properties. To shed light on free radical scavenging vs redox facets of such activity, we applied hydrogen atom transfer- and electron transfer-based assays to pristine Sepia ink, eumelanin from Sepia ink, chemically controlled eumelanins and their precursor building blocks. Our work contributes to the rational use of the antioxidant properties of eumelanin for health, cosmetics and environmental applications.

Solid adenine and seawater salts exposed to gamma radiation: An FT-IR and EPR spectroscopy analysis for prebiotic chemistry.

Solids of adenine obtained from distilled water and seawater lyophilized solutions were γ irradiated at a 94.52 kGy dose. Results indicate that pure solid adenine had a low degradation rate, likewise the solid containing seawater salts. However, EPR spectroscopy analysis suggests a high interaction of the radiation with seawater salts, by radical formation in sulfate ions. These outcomes are of interest for prebiotic chemistry, since ions could have played important roles in chemical evolution. In addition, Martian soil is rich in sulphate salts, thus these salts could protected organic molecules being degraded by γ-radiation.

Melanins and melanogenesis: from pigment cells to human health and technological applications.

During the past decade, melanins and melanogenesis have attracted growing interest for a broad range of biomedical and technological applications. The burst of polydopamine-based multifunctional coatings in materials science is just one example, and the list may be expanded to include melanin thin films for organic electronics and bioelectronics, drug delivery systems, functional nanoparticles and biointerfaces, sunscreens, environmental remediation devices. Despite considerable advances, applied research on melanins and melanogenesis is still far from being mature. A closer intersectoral interaction between research centers is essential to raise the interests and increase the awareness of the biomedical, biomaterials science and hi-tech sectors of the manifold opportunities offered by pigment cells and related metabolic pathways. Starting from a survey of biological roles and functions, the present review aims at providing an interdisciplinary perspective of melanin pigments and related pathway with a view to showing how it is possible to translate current knowledge about physical and chemical properties and control mechanisms into new bioinspired solutions for biomedical, dermocosmetic, and technological applications.

Study of the influence of pigments in the polymerization and mechanical performance of commercial dental composites / Estudo sobre a influência dos pigmentos na polimerização e no desempenho mecânico dos compósitos dentais comerciais

Objective: The aim of this study was to analyze the influence of the amount of shade pigment and opacifying components inthe polymerization and mechanical properties in two brands of Brazilian dental resin composites. Material and Methods: Master Fill microhybrid resin for enamel (colorless and shades A2, A4), and Opallis for enamel and dentine, both shades A2. Thecomposite resins were photopolymerized by a LED device at 19.7 J. The mechanical properties were obtained through flexuralresistance (FR), compression strength (CS) and Vickers microhardness (VM); the degree of conversion (DC) was obtainedby FTIR and translucence was obtained by sphere espectrometer. Conclusion: The analysis indicated that resin with more colorpigments (MA4) or more opacity components (ODA2) hadlow polymerization and poor mechanical properties than clearer(M) or more translucent (OEA2) resins, indicating that betterperformance can be obtained by increasing the radiation dose.

Objetivo: O objetivo deste estudo era analisar a influênciada quantidade de pigmentos de cor e de componentes opacificantesna polimerização e nas propriedades mecânicas em duasmarcas Brasileiras de resinas compostas dentárias. Material e Métodos: Resina Master Fill, microhíbrida, para esmalte (incolore nas cores A2 e A4) e Opallis para esmalte e dentina, ambas na cor A2. As resinas foram fotoativadas por um aparelho diodo emissor de luz (LED) a 19.7 J. As propriedades mecânicas foram obtidas por resistência flexural, força de compressão, microdureza Vickers; o grau de conversão foi obtido por FTIR e a translucidez foi obtida por meio do Espectrômetro de Esfera. Conclusões: As análises indicaram que resinas com mais pigmentos decor (MA4) ou mais componentes opacificantes (ODA2) mostrarambaixa polimerização e pobre qualidade mecânica quandocomparadas às mais claras e/ou mais translúcidas, indicando que a dose de irradiação deve ser aumentada para obter melhor performance.