The electrocatalytic activity of a supramolecular assembly of CoTsPc/FeT4MPyP on multi-walled carbon nanotubes towards L-glutathione, and its determination in human erythrocytes

The electrocatalytic activity of a supramolecular complex based on cobalt(II) phthalocyanine tetrasulfonate and iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin adsorbed on multi-walled carbon nanotubes for the oxidation of L-glutathione (GSH) was investigated at pH 7.4. Scanning electron microscopy and energy dispersive X-ray spectrometry were used to characterize the morphologies and composition of the materials. The modified electrode displayed efficient electrocatalytic activity in terms of oxidation of GSH at an oxidation potential of 0 V (versus Ag/AgCl). Cyclic voltammetry and amperometry indicated that the oxidation involves 2-electrons, with a heterogeneous rate constant of 4.9?×?10⁵ mol^?1 L s^?1. The response is linear from 2 to 210 μmol ?L^-1, the sensitivity is 1570 μA L mmol^?1, the detection limit is 0.03 μmol L^?1, and the relative standard deviation of 110 μmol L^?1 GSH was 2.6% (n?=?10). The modified electrode was applied to the determination of GSH in erythrocytes and the results were in agreement with those obtained by a method reported in the literature.     

Isolation and Screening of Microorganisms for R-(+)-Limonene and (−)-β-Pinene Biotransformation

This work is focused on the biotransformation of R-(+)-limonene and (?)-β-pinene to bioflavor production. To carry out the present study, 405 microorganisms were tested for their ability to bioconvert the substrates. From the isolated microorganisms, 193 were selected in the prescreening using mineral medium for limonene degradation. At the screening step, eight strains were able to convert R-(+)-limonene and 15 to transform (?)-β-pinene, both in α-terpineol. The highest concentration in α-terpineol from R-(+)-limonene was about 3,450 mg/L for Penicillium sp. isolated from eucalyptus steam. From (?)-β-pinene, the highest product concentration of 675.5 mg/L was achieved using an Aspergillus sp. strain isolated from orange tree stem.     

Extractive Fermentation of Xylanase from Aspergillus tamarii URM 4634 in a Bioreactor

Of the many reported applications for xylanase, its use as a food supplement has played an important role for monogastric animals, because it can improve the utilisation of nutrients. The aim of this work was to produce xylanase by extractive fermentation in an aqueous two-phase system using Aspergillus tamarii URM 4634, increasing the scale of production in a bioreactor, partially characterising the xylanase and evaluating its influence on monogastric digestion in vitro. Through extractive fermentation in a bioreactor, xylanase was obtained with an activity of 331.4 U mL^?1 and 72 % yield. The xylanase was stable under variable pH and temperature conditions, and it was optimally active at pH 3.6 and 90 °C. Xylanase activity potentiated the simulation of complete monogastric digestion by 6 %, and only Mg²⁺ inhibited its activity. This process provides a system for efficient xylanase production by A. tamarii URM 4634 that has great potential for industrial use.     

Diphenyl Diselenide-Loaded Nanocapsules: Preparation and Biological Distribution

Over the past years, organoselenium compounds have been aimed as targets of interest in organic synthesis. Diphenyl diselenide [(PhSe)₂] is an important example of this class showing several pharmacological properties. However, the poor water-solubility and its low oral bioavailability may be considered an obstruction for the clinical utility of this compound. For this reason, the use of nanocapsules is a prominent approach to increase the bioavailability of lipophylic molecules. This study aims to prepare diphenyl diselenide-loaded nanocapsules with two different concentrations, by interfacial deposition of the preformed polymer in order to develop a system to improve its oral bioavailability. The drug-loaded nanocapsules with 1.56 and 5 mg ml^?1 and unloaded nanocapsule suspensions presented macroscopic homogeneous aspect, as well as submicronic sizes, low polydispersity, negative zeta potentials and slightly acid or neutral pH values. The biological tests of selenium distribution in different tissues of mice show a higher bioavailability of the (PhSe)₂ nanocapsules when compared with the free (PhSe)₂, both administered by per oral route at the dose of 50 mg/kg, showing a prominent influence of the nanocarries systems for biological properties of this organochalcogenium compound.     

Flow injection analysis of ethambutol in synthetic urine using a graphite-polyurethane composite electrode as an amperometric detector

Ethambutol (ETB) is a first-line antitubercular drug effective against actively growing Mycobacterium tuberculosis. Resistance of the mycobacterium to ethambutol among tuberculosis (TB) patients results from inadequate or inappropriate dosing of treatment or using low quality medication. It is therefore necessary to develop reliable methods for determining ethambutol metabolic profiles of patients at point of care for proper dosing. Herein an efficient ETB sensor device is illustrated. It consists of a graphite-polyurethane composite electrode. In order to characterise the electrochemical behaviour of ethambutol at pH = 8.0 voltammetric studies were performed. The detector was assembled in a flow injection apparatus and operated at +1.2 V (vs. Ag/AgCl(NaCl sat.)). The influence of sample volume and flow rate was studied. The linear response for the method was extended up to a 1.1 mmol L^?1 ethambutol solution with a detection limit of 0.0634 mmol L^?1. The reproducibility of current responses for injections of 0.7 mmol L^?1 ethambutol solution was evaluated to be 5.1% (n = 30) and the analytical frequency was 161 determinations h^?1. Two different samples were successfully analysed and the results were in good agreement with those obtained using capillary zone electrophoresis (CZE).      

Instrumental neutron activation analysis for assessing homogeneity of a whole rice candidate reference material

A whole rice reference material was prepared for use in quality control of trace elements in rice and in similar matrices. This study aimed at evaluating the homogeneity of the material. As, Br, Co, Cs, Fe, K, Na, Rb and Zn were determined in the samples by instrumental neutron activation analysis. The material is homogeneous for the elements determined (p < 0.05), except for Co and Fe, which presented dispersion of results much higher than the predicted degree of repeatability.     

Cure kinetics of epoxy composite applied on stator bars insulation

Cure kinetics study of epoxy resin composite, employed as stator bars insulation system, was evaluated through differential scanning calorimetry using the dynamic methodology, different heating rates. These experiments provided some important information about the system as activation energy (E _a = 65.4 kJ mol⁻¹), glass transition (T _g) values on different curing stages including the final cured material information and, besides that, it enables the comparison of these data with new materials under development. The activation energy value allows the determination of different energy needs of the system under evaluation, specially temperature for the material cure, improving the possibility of comparison between different insulation systems in use in the high voltage insulation business. The composite conversion degree based on the cure enthalpy (ΔH _cure) at different time of cure was also subject of analysis and from that it was possible to comprehend the cure pattern which allows the cure state prediction of further samples of this type of material and the more accurate evaluation of similar samples acquired directly from stator bars.     

Modulation of the pharmacological activities of secretory phospholipase A2 from Crotalus durissus cascavella induced by naringin

In this work we have characterized the action of the naringin, a flavonoid found in grapefruit and known for its various pharmacological effects, which include antioxidant blood lipid lowering and anticancer activity, on the structure and biochemical activities of a secretory phospholipase A (sPLA2) from Crotalus durissus cascavella, an important protein involved in the releasinge of arachidonic acid in phospholipid membranes. sPLA2 was incubated with naringin (mol:mol) at 37 °C and a discrete reduction in the UV scanning signal and a modification of the circular dichroism spectra were observed after treatment with naringin, suggesting modifications of the secondary structure of the protein. This flavonoid was able to decrease enzymatic activity and some pharmacological effects, such as myonecrosis, platelet aggregation, and neurotoxic activity caused by sPLA2, however, the inflammatory effect was not affected by naringin. In addition, small angle X-ray scattering (SAXS) data were collected for sPLA2 and naringin-treated sPLA2 to evaluate possible modifications of the protein structure. These structural investigations have shown that sPLA2 is an elongated dimer in solution and after treatment with naringin a conformational change in the dimeric configuration was observed. Our results suggest that structural modification may be correlated with the loss of enzymatic activity and alterations in pharmacological properties.     

Enzymatic catalyzed palm oil hydrolysis under ultrasound irradiation: Diacylglycerol synthesis

Diacylglycerol (DAG) rich oils have an organoleptic property like that of regular edible oils, but these oils do not tend to be accumulated as fat. Palm oil ranks first in the world in terms of edible oil production owing to its low cost. The aim of this study was to propose a new methodology to produce diacylglycerol by hydrolysis of palm oil using Lipozyme RM IM commercial lipase as a catalyst under ultrasound irradiation. The reactions were carried out at 55 °C with two different methods. First, the reaction system was exposed to ultrasonic waves for the whole reaction time, which led to enzymatic inactivation and water evaporation. Ultrasound was then used to promote emulsification of the water/oil system before the hydrolysis reaction, avoiding contact between the probe and the enzymes. An experimental design was used to optimize the ultrasound-related parameters and maximize the hydrolysis rate, and in these conditions, with a change in equilibrium, DAG production was evaluated.Better reaction conditions were achieved for the second method: 11.20 wt.% (water + oil mass) water content, 1.36 wt.% (water + oil mass) enzyme load, 12 h of reaction time, 1.2 min and 200 W of exposure to ultrasound. In these conditions diacylglycerol yield was 34.17 wt.%.     

Highly sensitive determination of salicylic acid in skin care product by means of carbon nanotube/iron oxide nanoparticle voltammetric sensors

Journal of Solid State Electrochemistry - The present work reports the performance and the mechanism of detection of a voltammetric sensor for salicylic acid (SA) in a skin care product employing a...