A simple, rapid method for the extraction of whole fire ant venom (Insecta: Formicidae: Solenopsis)

The invasive fire ant Solenopsis invicta is medically important because its venom is highly potent. However, almost nothing is known about fire ant venom proteins because obtaining even milligram-amounts of these proteins has been prohibitively challenging. We present a simple and fast method of obtaining whole venom compounds from large quantities of fire ants. For this, we separate the ants are from the nest soil, immerse them in dual-phase mixture of apolar organic solvent and water, and evaporate each solvent phase in separate. The remaining extract from the aqueous phase is largely made up of ant venom proteins. We confirmed this by using 2D gel electrophoresis while also demonstrating that our new approach yields the same proteins obtained by other authors using less efficient traditional methods. © 2013 Elsevier Ltd.

Dynamics and Conformational Studies of TOAC Spin Labeled Analogues of Ctx(Ile21)-Ha Peptide from Hypsiboas albopunctatus

Antimicrobial peptides (AMPs) isolated from several organisms have been receiving much attention due to some specific features that allow them to interact with, bind to, and disrupt cell membranes. The aim of this paper was to study the interactions between a membrane mimetic and the cationic AMP Ctx(Ile21)-Ha as well as analogues containing the paramagnetic amino acid 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid (TOAC) incorporated at residue positions n = 0, 2, and 13. Circular dichroism studies showed that the peptides, except for [TOAC13]Ctx(Ile21)-Ha, are unstructured in aqueous solution but acquire different amounts of α-helical secondary structure in the presence of trifluorethanol and lysophosphocholine micelles. Fluorescence experiments indicated that all peptides were able to interact with LPC micelles. In addition, Ctx(Ile21)-Ha and [TOAC13]Ctx(Ile21)-Ha peptides presented similar water accessibility for the Trp residue located near the N-terminal sequence. Electron spin resonance experiments showed two spectral components for [TOAC0]Ctx(Ile21)-Ha, which are most likely due to two membrane-bound peptide conformations. In contrast, TOAC2 and TOAC13 derivatives presented a single spectral component corresponding to a strong immobilization of the probe. Thus, our findings allowed the description of the peptide topology in the membrane mimetic, where the N-terminal region is in dynamic equilibrium between an ordered, membrane-bound conformation and a disordered, mobile conformation; position 2 is most likely situated in the lipid polar head group region, and residue 13 is fully inserted into the hydrophobic core of the membrane. © 2013 Vicente et al.

Determination of sildenafil and vardenafil by capillary zone electrophoresis using capacitively coupled contactless conductivity detection

A method based on capillary electrophoresis with capacitively coupled contactless conductivity detection (CE-C4D) for determination of two important phosphodiesterase type-5 inhibitors (sildenafil and vardenafil) is introduced. The background electrolyte (BGE) consisted of an aqueous solution of 500 mmol L-1 acetic acid, and the capillary was previously treated with polybrene solution to prevent cationic analytes from adsorbing onto the inner surface. Although the analytes migrate in the counter flow, the total time is short. An instrument with two C4D detectors allowed a seamless transition from a fast method (less than one minute) but of low-efficiency using the first detector to a more efficient method using the second detector. The analysis of commercial tablets showed no significant difference between CE-C4D and HPLC methods. Conductivity detection is a well-known low selectivity detection scheme, which in conjunction with the high mobility of the co-ion in the BGE (hydroxonium) allows one to predict that other cationic analogues of sildenafil can also be detected. This is an interesting feature given the increasing number of compounds in this class. © 2013 The Royal Society of Chemistry.

Influence of ethanol, acidity and chloride concentration on the corrosion resistance of AISI 316L stainless steel

The influence of ethanol, sulfuric acid and chloride on the corrosion resistance of 316L stainless steel was investigated by means of polarization curves and electrochemical impedance spectroscopy measurements. Over the studied range, the steel corrosion potential was independent of H2SO 4 and NaCl concentrations in aqueous solution. On the other hand, in solution containing 65 wt.% ethanol and 35 wt.% water, the corrosion potentials were higher than those obtained in aqueous solution. Besides, the steel corrosion potential was affected by the addition of H2SO4 and NaCl in solution. In solutions with and without ethanol, plus 0.35 wt.% NaCl, the presence of 1 wt.% H2SO4 inhibited the appearance of pitting corrosion. © 2013 Sociedade Brasileira de Química.

Electrochemical Properties of Oxo-Manganese Complex Biomimicking Enzyme Active Sites and Its Electrocatalytic Application for Dopamine Determination

This work describes the characterization of the [Mn2 IV,IVO2(terpy)2(H2O)2]4+ complex in aqueous solution by UV-vis spectrophotometry, cyclic voltammetry, and linear sweep voltammetry with a rotating disk electrode. The pH effect, potential scan rate, effect of perfluorosulfonate polymer, and anion of supporting electrode on the electrochemical behavior of the modified electrode for better performance were investigated. The potential peak of the modified electrode was linearly dependent upon the ratio [ionic charge]/[ionic radius]. The modified electrode exerted an electrocatalytic effect on dopamine oxidation in aqueous solution with a decrease in the overpotential compared with the unmodified glassy carbon electrode. This way, the modified electrode showed an enzymatic biomimicking behavior. Tafel plot analyses were used to elucidate the kinetics and mechanism of dopamine oxidation. © 2013 Springer Science+Business Media New York.

The effects of water molecules on the electronic and structural properties of peptide nanotubes

The self-assembly of short amino acid chains appears to be one of the most promising strategies for the fabrication of nanostructures. Their solubility in water and the possibility of chemical modification by targeting the amino or carboxyl terminus give peptide-based nanostructures several advantages over carbon nanotube nanostructures. However, because these systems are synthesized in aqueous solution, a deeper understanding is needed on the effects of water especially with respect to the electronic, structural and transport properties. In this work, the electronic properties of l-diphenylalanine nanotubes (FF-NTs) have been studied using the Self-Consistent Charge Density-Functional-based Tight-Binding method augmented with dispersion interaction. The presence of water molecules in the central hydrophilic channel and their interaction with the nanostructures are addressed. We demonstrate that the presence of water leads to significant changes in the electronic properties of these systems decreasing the band gap which can lead to an increase in the hopping probability and the conductivity. © the Owner Societies 2013.

In vitro activity of pineapple extracts (Ananas comosus, Bromeliaceae) on Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

Measures to control the cattle tick, Rhipicephalus (Boophilus) microplus, based only on chemical products are becoming unsustainable, mainly because of the development of resistance. The objective of this study was to test the effect of the aqueous extract of pineapple skin (AEPS) and bromelain extracted from the stem (Sigma-Aldrich®, B4882) on engorged females and larvae of R. (B.) microplus in vitro. These substances were diluted in water and evaluated at eight concentrations. Engorged females were collected and distributed in groups of 10, with three repetitions for each treatment. After immersion in the solutions, the females were placed in an incubator for observation of survival, oviposition and larval hatching. The larval packet method was used, also with three repetitions with about 100 larvae each. The packets were incubated and the readings were performed after 24h. The estimated reproduction and efficacy of the solutions were calculated. The LC50 and LC90 were estimated using the Probit procedure of the SAS program. The eight concentrations were compared within each treatment by the Tukey test. For the experiment with engorged females, the most effective concentrations were 125, 250 and 500mg/mL: 33%, 48% and 59% for the AEPS and 27%, 51% and 55% for the bromelain. The LC50 and LC90 values were, respectively, 276 and 8691mg/mL for AEPS and 373 and 5172mg/mL for bromelain. None of the dilutions tested was effective against the larvae of R. (B.) microplus. This is the first report of the action of pineapple extracts or their constituents on cattle ticks. The results demonstrate that further studies regarding composition of tick cuticle, with evaluation of other solvents and formulations, should be conducted seeking to enhance the effect of pineapple extracts and compounds against this ectoparasite. © 2013 Elsevier Inc.

Rapid determination of furosemide by combined spot test/diffuse reflectance spectroscopy to detect doping in sport

This paper describes the development and application of a simple, cheap, and clean method for the quantification of furosemide in urine samples from athletes, to detect doping, using a combined spot test/diffuse reflectance spectroscopy procedure. The method is based on the complexation reaction of furosemide (5-(aminosulfonyl)-4-chloro-2-((furanylmethyl)amino)benzoic acid, dissolved in ethanol, with FeCl3 and the surfactant dodecyltrimethylammonium bromide (DTAB) in aqueous solution, yielding a colored compound on the surface of a filter paper. The reagent concentrations were optimized using a chemometric experimental design. The reflectometric measurements of the complex formed were carried out at 477nm. The linear range obtained was 1.65-9.00×10-3molL-1 of furosemide (R=0.997), and the detection and quantification limits were 4.9×10-4 and 1.62×10-3molL-1, respectively. The proposed method was successfully applied in the analysis of furosemide in spiked urine, demonstrating that it is a reliable alternative method for the detection of furosemide doping in sport. © 2012 Elsevier B.V..

Effect of soaking time on the photoluminescence properties of cerium oxide nanoparticles

The structural and photoluminescence properties at room temperature of CeO2 nanoparticles synthesized by a microwave-assisted hydrothermal method (MAH) under different soaking times on KOH mineralizer added to a cerium ammonium nitrate aqueous solution were undertaken. X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Fourier transform Raman (FT-Raman) and photoluminescence (PL) measurements were employed. XRD revealed that the nanoparticles are free of secondary phases and crystallize in the cubic structure. The UV/vis absorption spectroscopy suggested the presence of intermediate energy levels in the band gap of structurally ordered powders. The most intense PL emission was obtained for nanoparticles which represent a lower particle size. © 2013 Elsevier Ltd and Techna Group S.r.l.

Estruturação do Eumenine Mastroparano por dinâmica molecular em misturas de TFE-água

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Interação do peptídeo MP-I com micela de SDS em solução aquosa: um estudo por dinâmica molecular

Pós-graduação em Biofísica Molecular - IBILCE

Ciclo reprodutivo de machos de Dendropsophus minutus (Anura, Hylidae)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos do extrato bruto e da microcistina-LR em Lactuca sativa L. (Asteraceae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Estudos das propriedades estruturais de análogos substituídos com 'TRP POT.2,7 ou 24' do fragmento com 30 resíduos da região amino-terminal da Esticolisina II

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)