IF - Instituto de Física

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http://200.137.215.59//handle/ri/841

O IF - Instituto de Física, da Universidade Federal de Goiás, oferece Graduação em: Bacharelado em Física; Licenciatura em Física; Física Médica; e, Engenharia Física.

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14, 15-epoxygeranylgeraniol and extracts isolated from Pterodon emarginatus Vog. fruits: antitumor activity on glioblastoma cells
(2012-09) Hansen, Daiane; Nakahata, Adriana Miti; Haraguchi, Mitsue; Okamoto, Oswaldo Keith; Gonçalez, Edlayne; Alonso, Antonio
Plant-derived substances have traditionally played important roles in the treatment of human diseases, including of great significance to cancer therapy. Plants of the genus Pterodon (Fabaceae, Leguminosae), commonly known as ‘sucupira’, are disseminated throughout the central region of Brazil and have been used frequently in popular medicine. In recent years, interest in these plants has increased considerably. The biological effects of their extracts and pure metabolites have been investigated in several experimental models in vivo and in vitro. Until the present day, the antitumor effect of Pterodon plants on brain tumors is unknown. Therefore, the aim of this work was to investigate the action of P. emarginatus Vogel extracts and its fractions on glioblastoma cells. The hexane (HE), dichloromethane (DE) and ethanol (EE) extracts were obtained from seeds powder in each solvent. The diterpene 14,15-epoxygeranylgeraniol was obtained from HE fractionation. For tumorigenic assays, the extracts and fractions were added to U87MG, a human glioblastoma cells line. The cell viability assay showed that the proliferation of U87MG was inhibited by both extracts and the 14,15- epoxygeranylgeraniol. Further trials in vivo will help to confirm these results, and may contribute to generate natural compounds for the treatment of this type of cancer.
15N NMR shifts of eumelanin building blocks in water: a combined quantum mechanics/statistical mechanics approach
(2020) Oliveira, Leonardo Bruno Assis; Fonseca, Tertius Lima da; Cabral, Benedito Jose Costa
Theoretical results for the magnetic shielding of protonated and unprotonated nitrogens of eumelanin building blocks including monomers, dimers, and tetramers in gas phase and water are presented. The magnetic property in water was determined by carrying out Monte Carlo statistical mechanics sampling combined with quantum mechanics calculations based on the gauge-including atomic orbitals approach. The results show that the environment polarization can have a marked effect on nitrogen magnetic shieldings, especially for the unprotonated nitrogens. Large contrasts of the oligomerization effect on magnetic shielding show a clear distinction between eumelanin building blocks in solution, which could be detected in nuclear magnetic resonance experiments. Calculations for a π-stacked structure defined by the dimer of a tetrameric building block indicate that unprotonated N atoms are significantly deshielded upon π stacking, whereas protonated N atoms are slightly shielded. The results stress the interest of NMR experiments for a better understanding of the eumelanin complex structure.
2D quantitative imaging of magnetic nanoparticles by an ac biosusceptometry based scanning approach and inverse problem
(2021) Biasotti, Gabriel Gustavo de Albuquerque; Próspero, Andre Gonçalves; Alvarez, Marcelo Dante Tacconi; Liebl, Maik; Pinto, Leonardo Antonio; Soares, Guilherme Augusto; Bakuzis, Andris Figueiroa; Baffa Filho, Oswaldo; Wiekhorst, Frank; Miranda, José Ricardo de Arruda
The use of magnetic nanoparticles (MNPs) in biomedical applications requires the quantitative knowledge of their quantitative distribution within the body. AC Biosusceptometry (ACB) is a biomagnetic technique recently employed to detect MNPs in vivo by measuring the MNPs response when exposed to an alternate magnetic field. The ACB technique presents some interesting characteristics: non-invasiveness, low operational cost, high portability, and no need for magnetic shielding. ACB conventional methods until now provided only qualitative information about the MNPs’ mapping in small animals. We present a theoretical model and experimentally demonstrate the feasibility of ACB reconstructing 2D quantitative images of MNPs’ distributions. We employed an ACB single-channel scanning approach, measuring at 361 sensor positions, to reconstruct MNPs’ spatial distributions. For this, we established a discrete forward problem and solved the ACB system’s inverse problem. Thus, we were able to determine the positions and quantities of MNPs in a field of view of 5 5 1 cm3 with good precision and accuracy. The results show the ACB system’s capabilities to reconstruct the quantitative spatial distribution of MNPs with a spatial resolution better than 1 cm, and a sensitivity of 1.17 mg of MNPs fixed in gypsum. These results show the system’s potential for biomedical application of MNPs in several studies, for example, electrochemical-functionalized MNPs for cancer cell targeting, quantitative sensing, and possibly in vivo imaging.
A study of the thermodynamic principles and implementations of the quantum Otto engine
(Universidade Federal de Goiás, 2023-08-11) Costa, Rafael do Lago Souza; Céleri, Lucas Chibebe; Céleri, Lucas Chibebe; Pontes, Renato Borges; Carvalho, Vanuildo Silva de
This monography provides a comprehensive overview of classical and quantum thermodynamics. The classical formulations of thermodynamics are discussed in detail, including concepts such as energy and equilibrium, ideal gases and internal energy. Study the first and second laws of thermodynamics and their applications to mechanical work, heat engines and thermodynamic cycles. The present work also covers some quantum thermodynamics principles, including the use of density operators to describe pure and mixed states of quantum systems and the time evolution of these operators. The first law of quantum thermodynamics is introduced, along with the concepts of quantum adiabatic evolution and quantum Otto cycles. In addition, this monography briefly discusses the concept of Maxwell’s demon in the context of quantum thermodynamics and its implications for the second law. Overall, this work provides a comprehensive introduction to the basic principles of classical and quantum thermodynamics.
A temperature dependent ZGB-like model: entropic sampling simulations
(2022) Santos, E. D.; Ferreira, Lucas de Souza; Jorge, Lucas Nunes; Leão, Salviano de Araujo; Caparica, Álvaro de Almeida
By means of entropic sampling simulations we study a ZGB-like model. We consider an attractive nearest-neighbor CO–CO interaction when adsorbed on the system. We also take into account an attraction between oxygen atoms, but of lesser intensity. In analyzing the effect of the temperature increase in our catalytic system, we extract the temperature at which the output of CO is very large, which we call the critical desorption temperature. This output is abrupt, and our results lead to the conclusion that this transition from a CO poisoned state to a state in which the lattice sites are occupied by oxygen atoms, vacancies, and a few CO units, is a first order phase transition. A finite-size scaling analysis was performed to extract the critical desorption temperature for an infinite system.
AC biosusceptometry and magnetic nanoparticles to assess doxorubicin-induced kidney injury in rats
(2020) Próspero, André Gonçalves; Oliveira, Patrícia Fidelis de; Soares, Guilherme Augusto; Miranda, Milena F.; Pinto, Leonardo Antonio; Souza, Daniela Cristina dos; Silva, Vanessa dos Santos; Zufelato, Nícholas; Bakuzis, Andris Figueiroa; Miranda, José Ricardo de Arruda
Aim: This paper aims to investigate a doxorubicin (DOX) chronic kidney disease rat model using magnetic nanoparticles (MNPs) associated with the alternate current biosusceptometry (ACB) to analyze its different perfusion profiles in both healthy and DOX-injured kidneys. Materials & methods: We used the ACB to detect the MNP kidney perfusion in vivo. Furthermore, we performed biochemical and histological analyses, which sustained results obtained from the ACB system. We also studied the MNP biodistribution. Results: We found that DOX kidney injury alters the MNPs' kidney perfusion. These changes became more intense as the disease progressed. Moreover, DOX has an important effect on MNP biodistribution as the disease evolved. Conclusion: This study provides new applications of MNPs in nephrology, instrumentation, pharmacology, physiology and nanomedicine.
AC susceptibility as a tool to probe the dipolar interaction in magnetic nanoparticles
(2017) Landi, Gabriel Teixeira; Arantes, Fabiana Rodrigues; Reinaldo Cornejo, Daniel; Bakuzis, Andris Figueiroa; Andreu, Irene; Natividad, Eva
The dipolar interaction is known to substantially affect the properties of magnetic nanoparticles. This is particularly important when the particles are kept in a fluid suspension or packed within nano-carriers. In addition to its usual long-range nature, in these cases the dipolar interaction may also induce the formation of clusters of particles, thereby strongly modifying their magnetic anisotropies. In this paper we show how AC susceptibility may be used to obtain information regarding the influence of the dipolar interaction in a sample. We develop a model which includes both aspects of the dipolar interaction and may be fitted directly to the susceptibility data. The usual long-range nature of the interaction is implemented using a mean-field approximation, whereas the particle-particle aggregation is modeled using a distribution of anisotropy constants. The model is then applied to two samples studied at different concentrations. One consists of spherical magnetite nanoparticles dispersed in oil and the other of cubic magnetite nanoparticles embedded on polymeric nanospheres. We also introduce a simple technique to address the presence of the dipolar interaction in a given sample, based on the height of the AC susceptibility peaks for different driving frequencies.
Adjusting neutrino interaction models and evaluating uncertainties using NOvA near detector data
(2020) Acero Ortega, Mario A.; Adamson, P.; Agam, G.; Soplin, Leonidas Aliaga; Alion, T.; Allakhverdian, Vladimir; Anfimov, Nikolay; Antoshkin, A.; Asquith, Lily; Aurisano, Adam; Gomes, Ricardo Avelino
The two-detector design of the NOvA neutrino oscillation experiment, in which two functionally identical detectors are exposed to an intense neutrino beam, aids in canceling leading order effects of cross-section uncertain ties. However, limited knowledge of neutrino interaction cross sections still gives rise to some of the largest system atic uncertainties in current oscillation measurements. We show contemporary models of neutrino interactions to be discrepant with data from NOvA, consistent with discrep ancies seen in other experiments. Adjustments to neutrino interaction models in GENIE are presented, creating an effec tive model that improves agreement with our data. We also describe systematic uncertainties on these models, includ ing uncertainties on multi-nucleon interactions from a newly developed procedure using NOvA near detector data.
Albumin coating prevents cardiac effect of the magnetic nanoparticles
(2019) Nunes, Allancer Divino de Carvalho; Silva, Lorrany A. Gomes; Zufelato, Nícholas; Próspero, André Gonçalves; Quini, Caio César; Matos, Ronaldo Vitor Reis; Miranda, Jose Ricardo de Arruda; Bakuzis, Andris Figueiroa
We have showed that surface layer can determine cardiac effects of the magnetic nanoparticles (MNPs). Considering the high binding capacity of albumin and low side-effects, the aim of this study was to evaluate the influence of albumin coating on the cardiovascular effects of two manganese ferrite-based MNPs: citrate-coated and bare MNPs. Isolated rat hearts were perfused with citrate-coated magnetic nanoparticles (CiMNPs), citrate albumin-coated magnetic nanoparticles (CiAlbMNPs), bare magnetic nanoparticles (BaMNPs), and albumin-coated magnetic nanoparticles (AlbMNPs). CiMNPs induce a transient decrease in the left ventricular end-systolic pressure, +dP/dt and -dP/dt. These effects were not worsened by albumin coating. BaMNPs significantly increased the left ventricular end-diastolic pressure and perfusion pressure and decreased the +dP/dt and -dP/dt. These effects were completely absent in hearts perfused with AlbMNPs. None of the MNPs changed heart rate or arterial blood pressure in conscious rats. Magnetic signals in isolated hearts perfused with BaMNPs were significantly higher than AlbMNPs perfused hearts. However, the magnetic signal in heart tissue was similar when the MNPs were infused in conscious rats. These data indicate that albumin-coated can reduce cardiovascular effects of MNPs. These findings suggest a protective effect of albumin surface in MNPs, favoring its future therapeutic applications.
Alguns aspectos da optica quântica usando campos luminosos em modos viajantes
(2015) Valverde, Clodoaldo; Castro, Adailton Neres; Santos, E. P.; Baseia, Basílio
Although the theoretical treatment to describe the light field in quantum optics was generic, during large time it was predominantly related to optical modes trapped inside cavities. Important results were then obtained in this scenario. However, in view of the practical difficulties due to the deleterious effects of decoherence upon states of trapped fields, many physicists in this area began to focus more emphasis in the treatment using traveling fields. This brief report concerns with engineering non-classical states of light field to show some details and applications in the in the later scenario. Here the interaction “atom-trapped field”, is translated into the interaction “beam splitter-traveling field”.
An adaptive design approach for defects distribution modeling in materials from first-principle calculations
(2020) Lourenço, Maicon Pierre; Anastácio, Alexandre dos Santos; Rosa, Andreia Luisa da; Frauenheim, Thomas; Silva, Mauricio Chagas da
Designing and understanding the mechanism of non-stoichiometric materials with enhanced properties is challenging, both experimentally and even computationally, due to the large number of chemical spaces and their distributions through the material. In the current work, it is proposed a Machine Learning approach coupled with the Efficient Global Optimization (EGO) method—an Adaptive Design (AD)—to model local defects in materials from first-principle calculations. Our method takes into account the smallest sample set as possible, envisioning the material defect structure relationship with target properties for new insights. As an example, the AD framework allows us to study the stability and the structure of the modified goethite (Fe0.875Al0.125OOH) by considering a proper defect distribution, from first-principle calculations. The chemical space search for the modified goethite was evaluated by starting from different sizes and configurations of the samples as well as different surrogate models (ANN and Gaussian Process; GP), acquisition functions, and descriptors. Our results show that the same local solution of several defect arrangements in Fe0.875Al0.125OOH is found regardless of the initial sample and regression model. This indicates the efficiency of our search method. We also discuss the role of the descriptors in the accelerated global search for defects in material modeling. We conclude that the AD method applied in material defects is a successful approach in automating the search within huge chemical spaces from first-principle calculations by considering small samples. This method can be applied to mechanistic elucidation of non-stoichiometric materials, solid solutions, alloys, and Schottky and Frenkel defects, essential for material design and discovery.
An entropic simulational study of the spin-1 Baxter–Wu model in a crystal field
(2021) Jorge, Lucas Nunes; Martins, Paulo Henrique Lana; Silva, Cláudio José da; Ferreira, Lucas de Souza; Caparica, Álvaro de Almeida
We investigate the critical behavior of the two-dimensional spin-1 Baxter–Wu model in a crystal field using entropic sampling simulations, based on the Wang–Landau method, with the joint density of states. We obtain the temperature–crystal field phase diagram, which includes a tetracritical line ending at a pentacritical point. A finite-size scaling analysis of the maximum of the specific heat, while changing the crystal field anisotropy, is used to obtain a precise location of the pentacritical point. Our results give the critical temperature and crystal field as Tpc = 0.98030(10) and Dpc = 1.68288(62). We also detect that at the first-order region of the phase diagram, the specific heat exhibits a double peak structure as in the Schottky-like anomaly, which is associated with an order–disorder transition.
An EPR spin probe study of the interactions between PC liposomes and stratum corneum membranes
(2018) Mendanha Neto, Sebastião Antônio; Anjos, Jorge Luiz Vieira dos; Silva, Lorena Maione; Silva, Halanna Cristina Barbosa; Lima, Eliana Martins; Alonso, Antonio
The electron paramagnetic resonance (EPR) spin labeling methodology was used to analyze the interactions of phosphatidylcholine (PC) liposomal formulations that are commonly used as transepidermal drug delivery systems with stratum corneum (SC) membranes. The lipid dynamics of five liposome formulations were eval uated to study the influences of sorbitan monooleate (Span80), cholesterol, and cholesterol with the charged lipids 2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-distearoyl-sn-glycero-3-phospho-(1′-rac-gly cerol) (DSPG) on the molecular dynamics of PC vesicles. The EPR spectra of 5-doxyl-stearic acid (5-DSA) showed that the addition of Span80 to the liposomes increased the lipid fluidity, whereas cholesterol had the opposite effect, and the combination of charged lipids and cholesterol did not additionally influence the lipid bilayer dynamics. Fatty acid spin-labeled SC membranes were treated with the liposome formulations, leading to mi gration of the spin label to the molecular environment of the formulation and the presence of two spectral components representing distinct mobility states. In terms of molecular dynamics, these environments corre spond to the lipid domains of the untreated SC and the liposome, indicating a poor interaction between the liposome and SC membranes. However, the contact was sufficient to allow a pronounced exchange of the spin labeled fatty acid. Our data suggest that flexible liposomes may access the inner intercellular membranes of the SC and facilitate mutual lipid exchange without losing their relative liposomal integrity.
Analysis of the interactions of amphotericin B with the Leishmania plasma membrane using EPR spectroscopy
(2020) Alonso, Lais; Mendanha Neto, Sebastião Antônio; Dorta, Miriam Cristina Leandro; Alonso, Antonio
Electron paramagnetic resonance (EPR) spectroscopy of spin labels was used to study the interactions of amphotericin B (AmB) with the plasma membrane of Leishmania amazonensis promastigotes, erythrocytes, and J774 macrophages. Spin labels embedded into the cell membranes detected strong interactions with putative AmB/sterol complexes that resulted in pronounced changes in the EPR spectra, which can be interpreted as a reduction in membrane fluidity or an increase in the polarity assessed by the spin probe. The EPR spectra of spin-labeled lipids corroborated the findings that AmB does not enter phospholipid membrane-sterol models and probably forms extramembranous aggregates, as predicted by the sterol sponge model. Furthermore, these aggregates were shown to extract the spin probe androstanol from the lipid bilayer. However, in contrast to the results for the model membrane, EPR spectroscopy suggested that AmB easily enters the membranes of the studied cells, implying that the entry process is dependent on interactions with the membrane proteins.
Anderson localization in the quintic nonlinear Schrödinger equation
(2016) Cardoso, Wesley Bueno; Leão, Salviano de Araujo; Avelar, Salviano de Araujo
In the present paper we consider the quintic defocusing nonlinear Schrödinger equation in presence of a disordered random potential and we analyze the effects of the quintic nonlinearity on the Anderson localization of the solution. The main result shows that Anderson localization requires a cutoff on the value of the parameter that controls the quintic nonlinearity, with the cutoff depending on the amplitude of the random potential.
Antiangiogenic potential of Jatropha curcas latex in the chick chorioallantoic membrane model
(2019) Almeida, Luciane Madureira de; Bailão, Elisa Flávia Luiz Cardoso; Pereira, Illana Reis; Alves, Fabrício Ferreira; D’Abadia, Patrícia Lima; Borges, Leonardo Luiz; Matos, Fabio Santos; Lino Junior, Ruy de Souza; Reis, Paulo Roberto de Melo; Gonçalves, Pablo José
AIMS: To perform a physicochemical and phytochemical characterization of Jatropha curcas latex and to investigate its antiangiogenic potential. METHODS: We performed an initial physicochemical characterization of J. curcas latex using thermal gravimetric analyses and Fourier Transform Infrared spectroscopy. After that, phenols, tannins and flavonoids were quantified. Finally, the potential of J. curcas latex to inhibit angiogenesis was evaluated using the chick chorioallantoic membrane model. Five groups of 20 fertilized chicken eggs each had the chorioallantoic membrane exposed to the following solutions: (1) water, negative control; (2) dexamethasone, angiogenesis inhibitor; (3) Regederm®, positive control; (4) 25% J. curcas latex diluted in water; (5) 50% J. curcas latex diluted in water; and (6) J. curcas crude latex. Analysis of the newly-formed vascular net was made through captured images and quantification of the number of pixels. Histological analyses were performed to evaluate the inflammation, neovascularization, and hyperemia parameters. The results were statically analyzed with a significance level set at p<0.05. RESULTS: Physicochemical characterization showed that J. curcas latex presented a low amount of cis-1.4-polyisoprene, which reduced its elasticity and thermal stability. Phytochemical analyses of J. curcas latex identified a substantial amount of phenols, tannins, and flavonoids (51.9%, 11.8%, and 0.07% respectively). Using a chick chorioallantoic membrane assay, we demonstrated the antiangiogenic potential of J. curcas latex. The latex induced a decrease in the vascularization of the membranes when compared with neutral and positive controls (water and Regederm®). However, when compared with the negative control (dexamethasone), higher J. curcas latex concentrations showed no significant differences. CONCLUSIONS: J. curcas latex showed low thermal stability, and consisted of phenols, tannins, and flavonoids, but little or no rubber. Moreover, this latex demonstrated a significant antiangiogenic activity on a chick chorioallantoic membrane model. The combination of antimutagenic, cytotoxic, antioxidant and antiangiogenic properties makes J. curcas latex a potential target for the development of new drugs.
Antigenotoxicity protection of Carapa guianensis oil against mitomycin C and cyclophosphamide in mouse bone marrow
(2017) Pontes, Susy Ricardo Lemes; Chaves, Dwight Assis; Silva Junior, Nelson Jorge da; Carneiro, Cristiene Costa; Lee, Chen Chen; Almeida, Luciane Madureira de; Gonçalves, Pablo José; Reis, Paulo Roberto de Melo
The aim of this study was to evaluate the possible protective of C. guianensis oil against MMC and CP, which are direct- and indirect-acting chemical mutagens, using the micronucleus test. Three experiments were performed. First the C. guianensis oil was co-administered to mice at doses of 250, 500 and 1000 mg/ kg bw with 4 mg/kg bw MMC or 50 mg/kg bw CP. Second, the mutagenic drug (CP) was administered ip 50 mg/kg bw and after 6 and 12 hours 250 and 500 mg/kg bw of C. guianensis oil were administered. In the last, C. guianensis oil was administrated (250 and 500 mg/kg bw) during five days and after it was administered ip 50 mg/kg bw CP. The results obtained showed that the C. guianensis oil is not cytotoxic neither genotoxic to mouse bone marrow. Regarding the antimutagenic effect, all doses of C. guianensis oil were significantly (p < 0.05) effective in reducing the frequency of micronucleated polychromatic erythrocytes, when compared with MMC or CP alone. Based on these results, our results suggest that the C. guianensis oil shows medicinal potential as an antimutagenic agent, modulating the mutagenicity caused by both direct- and indirect-acting chemical mutagens, in a mammalian model.
Antileishmanial activity of 3,4,5-trisubstituted isoxazoles by interaction with Leishmania amazonensis plasma membrane
(2022) Alonso, Lais; Pianoski, Karlos Eduardo; Alonso, Antonio; Rosa, Fernanda Andreia
The isoxazole core has been identified as an essential privileged structure in discovering new and potent leishmanicidal agents. Thus, the present study reports the in vitro activity of a series of thirty-five 3,4,5-trisubstituted isoxazole derivatives against the promastigote form of L. amazonensis. Cytotoxicity against macrophages, hemolysis activity, and the effect on the parasite membrane were also evaluated. The results show that eight compounds exhibited potent antileishmanial activity (IC50 < 20 μM). The compounds 2e and 3de, the most active of the series, caused a remarkable change in the fluidity of the parasite's membrane and exhibited low toxicity for mammalian cells.
Antileishmanial activity of the chalcone derivative LQFM064 associated with reduced fluidity in the parasite membrane as assessed by EPR spectroscopy
(2020) Alonso, Lais; Menegattic, Ricardo; Gomes, Rodrigo Saar; Dorta, Miriam Leandro; Luzin, Rangel Magalhães; Lião, Luciano Morais; Alonso, Antonio
A novel chalcone derivative, LQFM064, demonstrated antileishmanial activity against Leishmania (L.) amazonensis, with an IC50 value of ~10 μM for the promastigote form. Electron paramagnetic resonance (EPR) spectroscopy of a spin-labeled stearic acid incorporated in the plasma membrane of L. amazonensis promastigotes revealed that after 2 h of treatment with LQFM064, the parasite showed remarkable reductions in membrane fluidity. The features of the altered EPR spectra were similar to those reported for the erythrocyte membrane, which was suggested to be due to the cross-linking of oxidized hemoglobin with the cytoskeleton spectrin. In comparison to miltefosine (MIL), LQFM064 demonstrated a much lower hemolytic potential against both erythrocytes in PBS and whole blood, less cytotoxicity in J774.A1 macrophages and equivalent ability to kill parasites internalized in J774.A1 macrophages. Measurements of the IC50 values for assays with different cell concentrations enabled the estimation of the membrane-water partition coefficient (KM/W), as well as the concentrations of LQFM064 in membrane (cm50) and aqueous phase (cw50) that reduces the cell population by 50%. From the KM/W and cm50 values it was deduced that LQFM064 has a greater affinity than MIL for the parasite membrane, but the antiproliferative activity of both substances is exerted at a similar concentration in the plasma membrane.
Antileishmanial and cytotoxic activities of ionic surfactants compared to those of miltefosine
(2019) Alonso, Lais; Cardoso, Eder Jeferson Souza Cardoso; Gomes, Rodrigo Saar Gomes; Mendanha Neto, Sebastião Antônio; Dorta, Miriam Cristina Leandro; Alonso, Antonio
Using the electron paramagnetic resonance (EPR) of spin-labeled stearic acid and a spin label chemically attached to the membrane proteins, the interaction of miltefosine (MIL) and the ionic surfactants sodium dodecyl sulfate (SDS, anionic), cetyltrimethylammonium chloride (CTAC, cationic) and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS, zwitterionic) with the plasma membrane of Leishmania (L.) amazonensis promastigotes was studied. The spin-label EPR data indicated that the four compounds studied have the ability to increase the molecular dynamics of membrane proteins to a large extent. Compared to the other compounds, SDS produced the smallest increases in dynamics and demonstrated the lowest antileishmanial activity and cytotoxicity to J774.A1 macrophages. The activities of the other three compounds were not different from each other, but CTAC had a stronger activity against L. amazonensis promastigotes at higher cellular concentrations (> 1 × 109 cells/mL) and was the most effective against L. amazonensis-infected macrophages. However, CTAC was also the most cytotoxic to macrophages. By measuring the IC50/CC50 values for assays of different cell concentrations, we estimated the membrane-water partition coefficient (KM/W) as well as the concentrations in the membrane (cm50) and aqueous phase (cw50) of the compounds at their IC50/CC50. Compared to the other compounds, SDS showed the lowest value of KM/W and the highest value of cm50. In all experiments in this study, the data for the zwitterionic molecules HPS and MIL were not significantly different.

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