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The indiscriminate and, very often, incorrect use of pesticides in Brazil, as well as in other countries, results in severe levels of environmental pollution and intoxication of human life. Herein, we studied plasma membrane models (monolayer and bilayer) of the phospholipid Dioleoyl-sn-glycerol-3-phosphocholine (DOPC) using Langmuir films, and large (LUVs) and giant (GUVs) unilamellar vesicles, to determine the effect of the pesticides chlorantraniliprole (CLTP), isoxaflutole (ISF), and simazine (SMZ), used in sugarcane. CLTP affects the lipid organization of the bioinspired models of DOPC π-A isotherms, while ISF and SMZ pesticides significantly affect the LUVs and GUVs. Furthermore, the in vivo study of the gill tissue in fish in the presence of pesticides (2.0 × 10-10 mol/L for CLTP, 8.3 × 10-9 mol/L for ISF, and SMZ at 9.9 × 10-9 mol/L) was performed using optical and fluorescence images. This investigation was motivated by the gill lipid membranes, which are vital for regulating transporter activity through transmembrane proteins, crucial for maintaining ionic balance in fish gills. In this way, the presence of phospholipids in gills offers a model for understanding their effects on fish health. Histological results show that exposure to CLTP, ISF, and SMZ may interfere with vital gill functions, leading to respiratory disorders and osmoregulation dysfunction. The results indicate that exposure to pesticides caused severe morphological alterations in fish, which could be correlated with their impact on the bioinspired membrane models. Moreover, the effect does not depend on the exposure period (24h and 96h), showing that animals exposed to pesticides for a short period suffer irreparable damage to gill tissue. In summary, we can conclude that the harm caused by pesticides, both in membrane models and in fish gills, occurs due to contamination of the aquatic system with pesticides. Therefore, water quality is vital for the preservation of ecosystems.

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Polysaccharide-coated magnetic nanoparticles (MNPs) have been reported to show potential applications in many biomedical fields. In this report, we have studied the interactions between magnetite (Fe3O4) MNPs functionalized with polysaccharides (diethylamino-ethyl dextran, DEAE-D or chitosan, CHI) with different membranes models by Langmuir isotherms, incorporation experiments, and brewster angle microscopy (BAM). In this report, zwitterionic 1,2-distearoyl-sn-glycerol-3-phosphoethanolamine (DSPE) and anionic 1,2-distearoyl-sn-glycerol-3-phosphate (DSPA) phospholipid, were used to form membrane models. Incorporation experiments (π-t) as well as the compression isotherms demonstrate positive interactions between MNPs and DSPE or DSPA monolayers. The study assessed the impact of varying initial surface pressure on a preformed phospholipid monolayer to determine the maximum insertion pressure (MIP) and synergy. Our findings indicate that the primary driving force of the coated MNPs incorporation into the monolayer predominantly stems from electrostatic interaction. The drop in the subphase pH from 6.0 to 4.0 led to an enhancement of the MIP value for DSPA phospholipid monolayer. On the other hand, for DSPE, the drop in the pH does not affect the MIP values. Besides, the presence of a magnetic field induces an enhancement of the insertion process of the MNPs into DSPA preformed monolayer, demonstrating that a previous interaction between MNPs and phospholipid preformed monolayer needs to take place to enhance the incorporation process. This work opens novel perspectives for the research of the influence of magnetic fields on the incorporation of MNPs into model membranes.

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This study analyses the insertion of Chlorogenic acid (CGA) in phosphatidylcholine (PC) membranes enriched with cholesterol (Chol). While cholesterol decreases the area per lipid and increases the dipole potential, CGA increases and decreases these values, respectively. When CGA is inserted into cholesterol-containing DMPC membranes, these effects cancel out, resulting in values that overlap with those of DMPC monolayers without Chol and CGA. The presence of CGA also compensates the increase of dipole potential produced by Chol which can be explain as a consequence of the orientation of CGA molecule at the interphase opposing the cholesterol dipole moieties and water dipoles. This compensatory effect is less effective when lipids lack carbonyl groups (CO). When monolayers are composed by unsaturated PCs the Chol compensation is found at higher concentrations of CGA due to the direct interaction between CGA and Chol. These results suggest that cholesterol modulates the interaction and distribution of CGA in the lipid membrane, which may have implications for its biological activity.

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The aim of the present study was to carry out a serological survey to identify the seroprevalence of Lawsonia intracellularis in six Thoroughbred farms in the Southern region of the state of Rio Grande do Sul, Brazil. During 2019 and 2020, blood samples from 686 Thoroughbred horses were obtained from six different breeding farms. Horses were divided into groups according to age: (1) broodmares (>5 years), (2) two-year-old foals, (3) yearlings, and (4) 0-6 months-old foals. Blood samples were collected by venipuncture of the external jugular vein. The detection of antibodies (IgG) against L. intracellularis was performed by Immunoperoxidase Monolayer Assay. The detection of specific antibodies (IgG) against L. intracellularis in the evaluated population was 51%. The highest detection (86.8%) of IgG was in the broodmares category, while the lowest (5.2%) was in foals of 0-6 months of age. Regarding the farms, the Farm 1 had the highest (67.4%) prevalence of seropositivity against L. intracellularis, while Farm 4 had the lowest (30.6%). There was no record of clinical manifestation of Equine Proliferative Enteropathy in the sampled animals. The results of this study show the high seroprevalence of L. intracellularis in Thoroughbred farms in the Southern of Rio Grande do Sul, suggesting a large and continuous exposure to the agent.

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Defective molybdenum disulfide (MoS2) monolayers (MLs) modified with coinage metal atoms (Cu, Ag and Au) embedded in sulfur vacancies are studied at a dispersion-corrected density functional level. Atmospheric constituents (H2, O2 and N2) and air pollutants (CO and NO), known as secondary greenhouse gases, are adsorbed on up to two atoms embedded into sulfur vacancies in MoS2 MLs. The adsorption energies suggest that the NO (1.44 eV) and CO (1.24 eV) are chemisorbed more strongly than O2 (1.07 eV) and N2 (0.66 eV) on the ML with a cooper atom substituting for a sulfur atom. Therefore, the adsorption of N2 and O2 does not compete with NO or CO adsorption. Besides, NO adsorbed on embedded Cu creates a new level in the band gap. In addition, it was found that the CO molecule could directly react with the pre-adsorbed O2 molecule on a Cu atom, forming the complex OOCO, via the Eley-Rideal reaction mechanism. The adsorption energies of CO, NO and O2 on Au2S2, Cu2S2 and Ag2S2 embedded into two sulfur vacancies were competitive. Charge transference occurs from the defective MoS2 ML to the adsorbed molecules, oxidizing the later ones (NO, CO and O2) since they act as acceptors. The total and projected density of states reveal that a MoS2 ML modified with copper, gold and silver dimers could be used to design electronic or magnetic devices for sensing applications in the adsorption of NO, CO and O2 molecules. Moreover, NO and O2 molecules adsorbed on MoS2-Au2s2 and MoS2-Cu2s2 introduce a transition from metallic to half-metallic behavior for applications in spintronics. These modified monolayers are expected to exhibit chemiresistive behavior, meaning their electrical resistance changes in response to the presence of NO molecules. This property makes them suitable for detecting and measuring NO concentrations. Also, modified materials with half-metal behavior could be beneficial for spintronic devices, particularly those that require spin-polarized currents.

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This article developed a novel electrochemical immunosensor for the specific detection of aflatoxin B1 (AFB1). Amino-functionalized iron oxide nanoparticles (Fe3 O4 -NH2 ) were synthesized. Fe3 O4 -NH2 were chemically bound on self-assembly monolayers (SAMs) of mercaptobenzoic acid (MBA). Finally, polyclonal antibodies (pAb) were immobilized on Fe3 O4 -NH2 -MBA. The sensor system was evaluated through atomic force microscopy (AFM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). A reduction in the anodic and cathodic peak currents was observed after the assembly of the sensor platform. The charge transfer resistance (Rct ) was increased due to the electrically insulating bioconjugates. Then, the specific interaction between the sensor platform and AFB1 blocks the electron transfer of the [Fe(CN)6 ]3-/4- redox pair. The nanoimmunosensor showed a linear response range estimated from 0.5 to 30 µg/mL with a limit of detection (LOD) of 9.47 µg/mL and a limit of quantification (LOQ) of 28.72 µg/mL for AFB1 identification in a purified sample. In addition, a LOD of 3.79 µg/mL, a LOQ of 11.48 µg/mL, and a regression coefficient of 0.9891 were estimated for biodetection tests on peanut samples. The proposed immunosensor represents a simple alternative, successfully applied in detecting AFB1 in peanuts, and therefore, represents a valuable tool for ensuring food safety.

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Surface modification of magnetic nanoparticles (MNPs) has been reported to play a significant role in determining their interactions with cell membranes. In this research, the interactions between polymer functionalized (chitosan, CHI or diethylamino-ethyl dextran, DEAE-D) Fe3O4 MNPs, pharmaceutical drugs and model cell membranes were investigated by Langmuir isotherms and adsorption measurements. In this study, 1,2-distearoyl-sn-glycerol-3-phosphate (DSPA) phospholipid monolayers were used as cell membrane models. Insertion experiments demonstrate that diclofenac (DCFN) is not absorbed at the air-water interface, whereas triflupromazine (TFPZ) has a MIP (maximum insertion pressure) of 35 m Nm-1. The insertion of composites MNPs:TFPZ or DCFN has larger MIP values, indicating that the MNPs are adsorbed on the monolayer with the drugs. An Fe3O4@CHI:DCFN composite presented an MIP of 39 m Nm-1 and Fe3O4@DEAE-D:DCFN presented an impressive MIP of 67 mNm-1. In the case of TFPZ, the enhancement in the MIP values is also evident, being 42 mNm-1 for Fe3O4@CHI:TFPZ and 40 mNm-1 for Fe3O4@DEAE-D:DCFN composite. All MNPs:drugs composites have MIP values greater than commonly accepted membrane pressure values, indicating that MNPs:drugs can penetrate a cellular membrane. The fact that the composite MNPs:drugs present greater MIP values than separated compounds indicates that polymer-coated MNPs can act as good drug delivery systems.

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Lysicamine, an alkaloid with tumorigenic activity, was incorporated in cell membrane models made of lipid Langmuir monolayers. Dipalmitoylphosphocholine (DPPC), dioleoylphosphocholine (DOPC), and palmitoyloleoylcholine (POPC) represented non-tumorigenic cell membranes, and dipalmitoylphosphoserine (DPPS), dioleoylphosphoserine (DOPS), and palmitoyloleoylserine (POPS), tumorigenic ones. The monolayers were characterized by tensiometry, infrared spectroscopy, and Brewster Angle Microscopy (BAM). No significant shifts of the isotherms were observed for the saturated lipids (DPPC and DPPS), while for the others (DOPC, POPS, DOPS, and POPS), more significant changes were observed not only in the compression isotherms but also in the surface pressure-time curve for pre-compressed monolayers. The molecular organization, as well as the morphology of the drug-lipid monolayers, could be inferred with infrared spectroscopy and BAM. While the first revealed that the alkyl chain ordering changed upon lysicamine incorporation, the second showed how the drug could distinctly change the state of aggregation of molecular domains at the air-water interface. In conclusion, lysicamine could interact distinctly with each lipid at the air-water interface, showing the dependence not only on the lipid polar groups but also on the level of unsaturation of the alkyl chains.

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Knowing how a bioactive compound interacts with cell membranes is important to understand its effect at the molecular level. In this sense, this work aimed to study the interaction of lysicamine, an alkaloid with action against lung cancer cell lines, with lipid monolayers as cell membrane models. We employed two lipid mixtures: the first composed of 35% DOPC, 30% DOPE, 20% sphingomyelin, and 15% cholesterol as healthy cell membranes models (MM1), and the second replacing DOPC with DOPS as cancer cells models (MM2). The interaction of lysicamine with the monolayers was evaluated using tensiometry, Brewster angle microscopy (BAM), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). Lysicamine had interfacial effects in both membrane models. For MM 1, it expanded the lipid monolayer and changed the interfacial rheological properties, increasing the in-plane elasticity of the films. PM-IRRAS spectra suggested a higher conformational disorder of the alkyl chains of the lipids. For MM 2, lysicamine also shifted the isotherms to higher areas, expanding the monolayers, but with no significant alteration in their interfacial rheological properties. PM-IRRAS spectra also suggested higher disorder in the orientation of the lipid alkyl chains upon lysicamine incorporation. For both models, BAM did not show alteration in interfacial aggregation upon drug incorporation. In conclusion, changes in some interfacial properties of membrane models caused by lysicamine depend on the monolayer composition, which can be associated with its bioactivity in cellular membranes.

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Abstract Lipoprotein monitoring is desirable in the management of medical conditions such as atherosclerotic cardiovascular disease and coronary artery disease, in which controlling the concentration of these chylomicrons is crucial. Current clinical methods are complex and present poor reproducibility between laboratories. For these reasons, recent guidelines discard the assessment of low-density lipoprotein cholesterol (LDL-C) as a routine analysis during lipid-lowering therapies. Concerning the importance of monitoring this parameter, the authors present an electrochemical immunosensor constructed from a simple and easy-to-reproduce platform that allows detecting and quantifying LDL nanoparticles directly from human serum samples. The performance of the biosensor was studied by scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The biosensing platform displays good stability and linearity between 30 mg dL-1 and 135 mg dL-1 with a detection limit of 20 mg dL-1. The proposed biosensor can be easily employed for monitoring LDL concentration in clinical treatments.

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In this work, we present an electrochemical study of the boron cage monomercaptoundecahydro-closo-dodecaborate [B12H11SH]2- in solution and in a self-assembled monolayer over a polycrystalline gold electrode. Cyclic voltammetry of the anion [B12H11SH]2- in solution showed a shift in the peak potentials related to the redox processes of gold hydroxides, which evidences the interaction between the boron cage and the gold surface. For an Au electrode modified with the anion [B12H11SH]2-, cyclic voltammetry response of the probe Fe(CN)63-/Fe(CN)64- showed a ΔEp value typical for a surface modification. Electrochemical impedance spectroscopy presented Rtc and Cdl values related to the formation of a self-assembled monolayer (SAM). A comparison of electrochemical responses of a modified electrode with thioglycolic acid (TGA) reveals that the boron cage [B12H11SH]2- diminishes the actives sites over the Au surface due to the steric effects. Differential capacitance measurements for bare gold electrode and those modified with [B12H11SH]2- and (TGA), indicate that bulky thiols enhance charge accumulation at the electrode-solution interface. In addition to electrochemical experiments, DFT calculations and surface plasmon resonance measurements (SPR) were carried out to obtain quantum chemical descriptors and to evaluate the molecular length and the dielectric constant of the Boron cage. From SPR experiments, the adsorption kinetics of [B12H11SH]2- were studied. The data fit for a Langmuir kinetic equation, typical for the formation of a monolayer.

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Atomically thin two-dimensional (2D) materials have gained significant attention from the research community in the fabrication of high-performance optoelectronic devices. Even though there are various techniques to improve the responsivity of the photodetector, the key factor limiting the performance of the photodetectors is constrained photodetection spectral range in the electromagnetic spectrum. In this work, a mixed-dimensional 0D/2D SnS2-QDs/monolayer MoS2 hybrid is fabricated for high-performance and broadband (UV-visible-near-infrared (NIR)) photodetector. Monolayer MoS2 is deposited on SiO2/Si using chemical vapor deposition (CVD), and SnS2-QDs are prepared using a low-cost solution-processing method. The high performance of the fabricated 0D/2D photodetector is ascribed to the band bending and built-in potential created at the junction of SnS2-QDs and MoS2, which enhances the injection and separation efficiency of the photoexcited charge carriers. The mixed-dimensional structure also suppresses the dark current of the photodetector. The decorated SnS2-QDs on monolayer MoS2 not only improve the performance of the device but also extends the spectral range to the UV region. Photoresponsivity of the device for UV, visible, and NIR region is found to be ∼278, ∼ 435, and ∼189 A/W, respectively. Fabricated devices showed maximum responsivity under the visible region attributed to the high absorbance of monolayer MoS2. The response time of the fabricated device is measured as ∼100 ms. These results reveal that the development of a mixed-dimensional (0D/2D) SnS2-QDs/MoS2-based high-performance and broadband photodetector is technologically promising for next-generation optoelectronic applications.

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Although some atomically thin 2D semiconductors have been found to possess good thermoelectric performance due to the quantum confinement effect, most of their behaviors occur at a higher temperature. Searching for promising thermoelectric materials at room temperature is meaningful and challenging. Inspired by the finding of moderate band gap and high carrier mobility in monolayer GeP3, we investigated the thermoelectric properties by using semi-classical Boltzmann transport theory and first-principles calculations. The results show that the room-temperature lattice thermal conductivity of monolayer GeP3 is only 0.43 Wm-1K-1 because of the low group velocity and the strong anharmonic phonon scattering resulting from the disordered phonon vibrations with out-of-plane and in-plane directions. Simultaneously, the Mexican-hat-shaped dispersion and the orbital degeneracy of the valence bands result in a large p-type power factor. Combining this superior power factor with the ultralow lattice thermal conductivity, a high p-type thermoelectric figure of merit of 3.33 is achieved with a moderate carrier concentration at 300 K. The present work highlights the potential applications of 2D GeP3 as an excellent room-temperature thermoelectric material.

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Lawsonia intracellularis is a bacterium already described in several species and most prevalent in pigs, in which it causes enteric problems. Horses can also be affected, developing a disease known as equine proliferative enteropathy, which results from the proliferation of intestinal crypt cells in response to infection by the bacterium. Despite the existence of reports of the disease in several countries, including Brazil, there are still no reports of the disease or epidemiological studies of its occurrence in symptomatic or asymptomatic horses in the state of Paraná. Thus, the present study was conducted to examine the occurrence of L. intracellularis in asymptomatic horses raised in the west, northwest and north regions of Paraná by means of serological testing and the real-time polymerase chain reaction (qPCR) technique. In the serological approach, the immunoperoxidase monolayer assay (IPMA) technique was employed. Feces were processed and subjected to qPCR. In total, samples were collected from 162 animals from 20 farms. Of these, 9/162 (5.55%) showed specific antibodies against L. intracellularis. Real-time PCR, on the other hand, identified 7/162 (4.32%) fecal samples positive for the presence of the bacterium. When the techniques were compared, none of the samples was positive by both, demonstrating that, for a better diagnosis, they must be performed together. In contrast to most reports in horses, the present studyde scribes higher serological and molecular occurrence in animals older than two years. These results are of great epidemiological relevance, as they indicate that the bacterium is present in the sampled regions of the state of Paraná. Therefore, the disease must be included in the differential diagnosis of diseases with similar clinical manifestations.(AU)

Lawsonia intracellularis é uma bactéria já descrita em várias espécies, sendo mais comum em suínos, ocasionando problemas entéricos nesses animais. Dentre estes, equinos podem ser acometidos, levando à uma doença conhecida como Enteropatia Proliferativa Equina que é decorrente da proliferação das células da cripta intestinal em reação à infecção pela bactéria. Apesar de existirem relatos da doença em diversos países, inclusive no Brasil, no estado do Paraná ainda não se tem relatos da doença e estudos epidemiológicos da ocorrência em equinos sintomáticos ou assintomáticos. O objetivo do presente estudo foi avaliar a ocorrência de L. intracellularis em equinos assintomáticos criados nas regiões Oeste, Noroeste e Norte do estado do Paraná através de sorologia e qPCR. Para a sorologia, utilizou-se a técnica da Imunoperoxidase em Monocamadas (IPMA). As fezes foram processadas e submetidas à técnica de Reação em Cadeia pela Polimerase em Tempo Real (qPCR). Ao todo, foram coletadas amostras de 162 animais de 20 propriedades. Destas, 9/162 (5,55%) apresentaram anticorpos específicos contra L. intracellularis. Já a qPCR, identificou 7/162 (4,32%) amostras de fezes positivas para a presença da bactéria. Ao se comparar as técnicas, nenhuma amostra foi positiva em ambas, demonstrando que, para um melhor diagnóstico, as mesmas devem ser realizadas em conjunto. Em contraste à grande parte dos relatos em equinos, o presente estudo encontrou uma maior ocorrência sorológica e molecular em animais com mais de dois anos de idade. Esses resultados são de grande relevância epidemiológica, pois indicam que a bactéria está presente nas regiões amostradas do estado do Paraná, levando à necessidade de incluir a doença no diagnóstico diferencial de enfermidades que cursam com manifestações clínicas semelhantes.(AU)

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Lawsonia intracellularis is a bacterium already described in several species and most prevalent in pigs, in which it causes enteric problems. Horses can also be affected, developing a disease known as equine proliferative enteropathy, which results from the proliferation of intestinal crypt cells in response to infection by the bacterium. Despite the existence of reports of the disease in several countries, including Brazil, there are still no reports of the disease or epidemiological studies of its occurrence in symptomatic or asymptomatic horses in the state of Paraná. Thus, the present study was conducted to examine the occurrence of L. intracellularis in asymptomatic horses raised in the west, northwest and north regions of Paraná by means of serological testing and the real-time polymerase chain reaction (qPCR) technique. In the serological approach, the immunoperoxidase monolayer assay (IPMA) technique was employed. Feces were processed and subjected to qPCR. In total, samples were collected from 162 animals from 20 farms. Of these, 9/162 (5.55%) showed specific antibodies against L. intracellularis. Real-time PCR, on the other hand, identified 7/162 (4.32%) fecal samples positive for the presence of the bacterium. When the techniques were compared, none of the samples was positive by both, demonstrating that, for a better diagnosis, they must be performed together. In contrast to most reports in horses, the present studyde scribes higher serological and molecular occurrence in animals older than two years. These results are of great epidemiological relevance, as they indicate that the bacterium is present in the sampled regions of the state of Paraná. Therefore, the disease must be included in the differential diagnosis of diseases with similar clinical manifestations.

Lawsonia intracellularis é uma bactéria já descrita em várias espécies, sendo mais comum em suínos, ocasionando problemas entéricos nesses animais. Dentre estes, equinos podem ser acometidos, levando à uma doença conhecida como Enteropatia Proliferativa Equina que é decorrente da proliferação das células da cripta intestinal em reação à infecção pela bactéria. Apesar de existirem relatos da doença em diversos países, inclusive no Brasil, no estado do Paraná ainda não se tem relatos da doença e estudos epidemiológicos da ocorrência em equinos sintomáticos ou assintomáticos. O objetivo do presente estudo foi avaliar a ocorrência de L. intracellularis em equinos assintomáticos criados nas regiões Oeste, Noroeste e Norte do estado do Paraná através de sorologia e qPCR. Para a sorologia, utilizou-se a técnica da Imunoperoxidase em Monocamadas (IPMA). As fezes foram processadas e submetidas à técnica de Reação em Cadeia pela Polimerase em Tempo Real (qPCR). Ao todo, foram coletadas amostras de 162 animais de 20 propriedades. Destas, 9/162 (5,55%) apresentaram anticorpos específicos contra L. intracellularis. Já a qPCR, identificou 7/162 (4,32%) amostras de fezes positivas para a presença da bactéria. Ao se comparar as técnicas, nenhuma amostra foi positiva em ambas, demonstrando que, para um melhor diagnóstico, as mesmas devem ser realizadas em conjunto. Em contraste à grande parte dos relatos em equinos, o presente estudo encontrou uma maior ocorrência sorológica e molecular em animais com mais de dois anos de idade. Esses resultados são de grande relevância epidemiológica, pois indicam que a bactéria está presente nas regiões amostradas do estado do Paraná, levando à necessidade de incluir a doença no diagnóstico diferencial de enfermidades que cursam com manifestações clínicas semelhantes.

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Structural, electronic, binding energies and magnetic properties of aluminum-doped and single vacancy blue phosphorene interacting with pollutant molecules are investigated using the density functional theory (DFT) with periodic boundary conditions. Acetylene, ozone, sulfur trioxide, hydrogen selenide, and sulfur dichloride molecules are considered to show the efficiency and enhancement of the sensing properties in comparison with the pristine blue phosphorene. Acetylene, sulfur trioxide, hydrogen selenide, and sulfur dichloride show chemisorption (> 0.5 eV/molecule) when interacting with the aluminum-doped system, but the ozone molecule dissociates in all configurations and symmetry sites. On the other hand, the acetylene, ozone, and sulfur trioxide with the single vacancy blue phosphorene exhibit chemisorption, the hydrogen selenide molecule exhibit a weak interaction energy, and the sulfur dichloride dissociates in all configurations and symmetry sites. In all the cases, the enhancement in the interaction energy was achieved when compared to other results for the same molecules. Finally, the single vacancy blue phosphorene shows a magnetic moment of ~1 µB/supercell, as induced by the vacancy.

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This article investigates the main aspects of the surface chemistry properties of the lactate oxidase (LacOx) enzyme monolayer at the air-subphase interface. Surface chemistry study determined the important properties like the surface packing and stability of the formed layer, whereas the spectroscopic experiments provided information regarding its secondary structure conformation of the enzyme. We have demonstrated that the LacOx in the monolayer form remained active for extended time period. In accordance to the data obtained from the isotherm it was also found that LacOx forms a stable monolayer that does not aggregate at the air-subphase interface. The stability of the monolayer at the air-subphase interface was studied by using compression-decompression cycles which revealed the stability with no significant evidence of aggregates or irreversible domains. This was further confirmed by UV-vis absorption and fluorescence measurements. Spectra from circular dichroism (CD) showed that the LB film retains the characteristic of an α-helix conformation.

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Plant-based biomass (CFB (carnauba fruit biomass)) obtained from the fruit exocarp of the species Copernicia prunifera (Mill.) H.E. Moore (carnauba) was evaluated for its viability as an adsorbent of potentially toxic metals in aqueous medium. The CFB was characterized by powder X-ray spectroscopy (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and zeta potential to investigate the morphology of the biosorbent and its interaction with water soluble metal ions of Pb and Cd. The biomass presents an amorphous structure, with negative zeta potential (- 2.59 mV), and the presence of functional groups such as O-H, C-O-C, C-H, and C=O. The removal potential of Pb(II) and Cd(II) was performed in a batch system, and monoelement solutions were tested to assess the effects of adsorbent dose and initial metal ion concentration, pH at the point of zero charge (pHPZC), sorption kinetics, and adsorption capacity. The most appropriate adsorbent concentration was 5 g/L, and sorption studies were carried out at pH 5.0 (pHPZC = 4.68), in which the surface of the adsorbent shows negative charges and favors the adsorption of metal ions. Kinetic studies showed that the pseudo-second order model best fit the experimental data, and equilibrium was reached at 120 min of contact time. The experimental sorption capacity (SCexp) for Pb and Cd was around 28 and 34 mg/g, respectively, and six different non-linear isotherm models were used to describe the sorption phenomena, among them, four with 2 parameters, i.e., Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (DR), respectively, and two with 3 parameters, namely, SIPS and Hill. The non-linear Temkin and Freundlich isotherm models best fit the experimental data for Pb(II) and Cd(II), respectively. According to the Langmuir model, Qmax was 26 mg/g and 58 mg/g for Pb(II) and Cd(II), respectively, indicating the efficiency of CFB as a new alternative to conventional methods for the removal of potentially toxic metals from aqueous medium.

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The insecticidal activity of Mentha oil and its main components has been tested and established for various insects/pests. Several mint ketones have demonstrated to act on GABAA receptors (GABAA-R), a transmembrane channel target of several important insecticides whose activity can be modulated by surface-active compounds and by changes in the physical properties of the lipid membrane. In the present work, we analyze the capacity of monoterpenic ketones most commonly found in Mentha species, pulegone and menthone, to interact with DPPC membranes by molecular dynamics (MD) simulations and Langmuir monolayers. The experimental results indicate that the presence of menthone and pulegone in the subphase modify the interfacial characteristics of DPPC isotherms. The changes were reflected as expansion of the isotherms and disappearance or bringing forward of DPPC phase transition. MD simulation corroborate these results and indicate that both ketones are located at the region of the carbonyl group, at the interface with the acyl chains. Ketone intercalation between lipid molecules would induce an increasing intermolecular interaction, diminishing the film elasticity and causing an ordering effect. Our results suggest that the insecticidal activity of both ketones could involve their interaction with lipid molecules causing disturbance of the cell membrane as postulated for several larvicide compounds, or at least modulating the receptor surrounding.

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This study investigates the main aspects of the surface behavior of the native phenylalanine dehydrogenase (PheDH) enzyme at the air/aqueous interface employing a saline subphase to induce the enzyme surface activity. Surface chemistry experiments were performed in order to determine the surface packing and stability of the formed layer, while spectroscopic experiments provided information regarding its secondary structure conformation. It was found that the PheDH enzyme forms a fluid film, which is quite homogeneous throughout its entire compression, being stable for long periods of time with no significant evidence of aggregates or irreversible domains during interfacial compression/decompression processes. The main secondary structures of the interfacial PheDH film were accessed via in situ reflectance-absorbance infrared spectroscopy, indicating a majority presence of α-helices, which were maintained after the film transfer to solid muscovite supports. The immobilized films presented a homogeneous and regular deposition, with controlled roughness and a mean thickness in the range of 8-10 nm.