santiago moreira - Academia.edu (original) (raw)

Papers by santiago moreira

Journal of Inorganic Biochemistry, 2005

The mechanism of activation thioamide-pyridine anti-tuberculosis prodrugs is poorly described in ... more The mechanism of activation thioamide-pyridine anti-tuberculosis prodrugs is poorly described in the literature. It has recently been shown that ethionamide, an important component of second-line therapy for the treatment of multi-drug-resistant tuberculosis, is activated through an enzymatic electron transfer (ET) reaction. In an attempt to shed light on the activation of thioamide drugs, we have mimicked a redox process involving the thionicotinamide (thio) ligand, investigating its reactivity through coordination to the redox reversible [Fe III/II (CN) 5 (H 2 O)] 2À/3À metal center. The reaction of the Fe III complex with thionicotinamide leads to the ligand conversion to the 3-cyanopyridine species coordinated to a Fe II metal center. The rate constant, k et = 10 s À1 , was determined for this intra-molecular ET reaction. A kinetic study for the cross-reaction of thionicotinamide and [Fe(CN) 6 ] 3À was also carried out. The oxidation of thionicotinamide by [Fe(CN) 6 ] 3À leads to formation of mainly 3-cyanopyridine and [Fe(CN) 6 ] 4À with a k et = (5.38 ± 0.03) M À1 s À1 at 25°C, pH 12.0. The rate of this reaction is strongly dependent on pH due to an acid-base equilibrium related to the deprotonation of the R-SH functional group of the imidothiol form of thionicotinamide. The kinetic results reinforced the assignment of an intra-molecular mechanism for the ET reaction of [Fe III (CN) 5 (H 2 O)] 2À and the thioamide ligand. These results can be valuable for the design of new thiocarbonyl-containing drugs against resistant strains of Mycobacterium tuberculosis by a self-activating mechanism.

Journal of Insect Behavior, 2011

In spite of the fact that studies concerning the mate choice by females have largely been based o... more In spite of the fact that studies concerning the mate choice by females have largely been based on the idea of the unanimity of the preference for certain male characteristics, variations in this behavior have been reported. Considering this aspect, we studied the influence of female age on mate choice and on the acceptance of courting by males of different ages in lab-reared medflies. The effects of the age of both sexes on the total courtship duration and on the behavioral units performed by males were also examined. Our results demonstrated that: (1) 4 to 12 day-old females prefer younger males; (2) 20 day-old females were less selective; (3) the acceptance of courting was not influenced by male age neither by the duration of behavioral units of courtship; (4) only the duration of continuous wing vibration was affected by the age of both sexes.

Archives of Oral Biology, 2009

Journal of The Brazilian Chemical Society, 2010

Trans-[Ru(L)(NH3)4(L)](PF6)n type complexes, where L = 4-cyanopyridine (CNpy), NCS-, CN-, and L... more Trans-[Ru(L)(NH3)4(L)](PF6)n type complexes, where L = 4-cyanopyridine (CNpy), NCS-, CN-, and L = CNpy, 1,4-dithiane (1,4-dt), 4-mercaptopyridine (pyS) and thionicotinamide (tna), were synthesized and characterized. SAMs on gold of the complexes containing sulfur were studied by reductive desorption and SERS spectroscopy. Depending on the nature of L, the withdrawing capability of the CNpy ligand is strong enough to partially oxidize the ruthenium atom and, as a consequence, delocalize the s electronic density from the trans located ligand. The reductive desorption results showed that the stability of the SAMs is directly related to this effect.

Journal of Power Sources, 2005

In this work, the water-gas shift (WGS) and the CO methanation reactions on a Co/γ-Al2O3 catalyst... more In this work, the water-gas shift (WGS) and the CO methanation reactions on a Co/γ-Al2O3 catalyst and the coupling of these reactors to a proton exchange membrane fuel cell were investigated. Results of chromatographic analyses showed that when the reactors are fed with a H2/CO (1000ppm) mixture, high conversions of CO into methane (90%) or CO2 (83%) are observed for

Biochimica Et Biophysica Acta-general Subjects, 2007

The effects of two ionic surfactants on the oligomeric structure of the giant extracellular hemog... more The effects of two ionic surfactants on the oligomeric structure of the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp) in the oxy -form have been studied through the use of several spectroscopic techniques such as electronic optical absorption, fluorescence emission, light scattering, and circular dichroism. The use of anionic sodium dodecyl sulphate (SDS) and cationic cethyltrimethyl ammonium chloride (CTAC) has allowed to differentiate the effects of opposite headgroup charges on the oligomeric structure dissociation and hemoglobin autoxidation. At pH 7.0, both surfactants induce the protein dissociation and a significant oxidation. Spectral changes occur at very low CTAC concentrations suggesting a significant electrostatic contribution to the protein-surfactant interaction. At low protein concentration, 0.08 mg/ml, some light scattering within a narrow CTAC concentration range occurs due to protein-surfactant precipitation. Light scattering experiments showed the dissociation of the oligomeric structure by SDS and CTAC, and the effect of precipitation induced by CTAC. At higher protein concentrations, 3.0 mg/ml, a precipitation was observed due to the intense charge neutralization upon formation of ion pair in the proteinsurfactant precipitate. The spectral changes are spread over a much wider SDS concentration range, implying a smaller electrostatic contribution to the protein-surfactant interactions. The observed effects are consistent with the acid isoelectric point (pI) of this class of hemoglobins, which favors the intense interaction of HbGp with the cationic surfactant due to the existence of excess acid anionic residues at the protein surface. Protein secondary structure changes are significant for CTAC at low concentrations while they occur at significantly higher concentrations for SDS. In summary, the cationic surfactant seems to interact more strongly with the protein producing more dramatic spectral changes as compared to the anionic one. This is opposite as observed for several other hemoproteins. The surfactants at low concentrations produce the oligomeric dissociation, which facilitates the iron oxidation, an important factor modulating further oligomeric protein dissociation.

Electronic Notes in Theoretical Computer Science, 2007

This paper defines the basis for the implementation in CASL (Common Algebraic Specification Langu... more This paper defines the basis for the implementation in CASL (Common Algebraic Specification Language) of an interval library such that intervals behave as real numbers endowed with an error information. To achieve that, we redefine the notion of interval local set defined in in such a way that it can be implemented in the underlying logic of CASL. With these results, it is possible to manipulate intervals in CASL, as if they were real numbers, with equational reasoning, and get an error estimation on the obtained results for free (from the width of the resulting interval). The paper describes the CASL definition of the interval library and presents a case study on a simple example requiring handling data with "tolerance" margin.

Innovative Food Science & Emerging Technologies, 2001

Highly acceptable snack products were obtained by extrusion cooking of admixed defatted chickpea,... more Highly acceptable snack products were obtained by extrusion cooking of admixed defatted chickpea, corn and bovine lung flours. These snacks had high quality protein content and provided 30᎐40% of the iron RDA for children. A nutritional protein assay of pure chickpea and lungrchickpea mixed snacks revealed that they presented similar NPRs. The final product obtained, a chickpearbovine lungrcorn snack, reduced to acceptable levels the prevalence of anaemia among the population of young children in creches of a poor Brazilian region. Sensory analysis showed a high acceptability for these snacks that was comparablè to commercial brands. The present work shows that it is possible to produce a highly acceptable snack of high nutritional quality that can be useful in nutritional programs against anaemia and malnutrition. ᮊ

Journal of Inorganic Biochemistry, 2006

Iron(III) meso-tetrakis (4-N-methylpyridiniumyl) porphyrin (FeTMPyP) undergoes a complex equilibr... more Iron(III) meso-tetrakis (4-N-methylpyridiniumyl) porphyrin (FeTMPyP) undergoes a complex equilibrium in aqueous solution as a function of pH. Use of phosphate buffers, a common practice in biomedical applications of porphyrins, suggests the complexation of phosphate anion at the sixth coordination position to the iron, which contributes to the complexity of the equilibrium in the pH range from 1 to 4. In the absence of phosphate the equilibrium is simplified in a similar way as in the presence of high salt concentrations. Combined use of optical absorption, 1 H NMR and infrared spectroscopies, together with the literature data, suggest the formation of hexacoordinated monoaqueous-phosphate FeTMPyP complex in a limited acidic pH range. Discussion of the behavior of cationic FeTMPyP as compared to anionic iron(III) meso-tetrakis (4-sulfonatophenyl) porphyrin (FeTPPS 4 ) is presented in regard to equilibrium of different species to explain the observed complex equilibrium.

Journal of Biotechnology, 1997

Twenty-five white rot fungal strains were tested for their ability to bleach Eucalyptus globulus ... more Twenty-five white rot fungal strains were tested for their ability to bleach Eucalyptus globulus oxygen delignified kraft pulp (OKP). Under nitrogen-limited culture conditions, eight outstanding biobleaching strains were identified that increased the brightness of OKP by more than 10 ISO units compared to pulp incubated in sterile control medium. The highest brightness gain of approximately 13 ISO units was obtained with Bjerkandera sp. strain BOS55, providing a high final brightness of 82% ISO. This strain also caused the greatest level of delignification, decreasing the kappa number of OKP by 29%. When the white rot fungal strains were tested in nitrogen-sufficient medium, the extracellular activities of laccase and peroxidases increased in many strains; nonetheless, the pulp handsheets were either destroyed or brightness gains were lower than those obtained under nitrogen-limitation. The titer of ligninolytic enzymes was not found to be indicative of biobleaching potential. However, the best biobleaching strains were generally characterized by a predominance of manganese dependent peroxidase (MnP) activity compared to other ligninolytic enzymes and by a high decolorizing activity towards the polyanthraquinone ligninolytic indicator dye, Poly R-478. © 1997 Elsevier Science B.V.

Biogeosciences, 2011

In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany) but also... more In the last decades, the mining exploitation of large areas in Lusatia (Eastern Germany) but also in other mining areas worldwide has led to the formation of hundreds of pit lakes. Pyrite oxidation in the surrounding dumps makes many such lakes extremely acidic (pH < 3). The biogeochemical functioning of these lakes is mainly governed by cycling of iron. This represents a relevant ecological problem and intensive research has been conducted to understand the involved biogeochemical processes and develop bioremediation strategies. Despite some studies reporting the presence of living organisms (mostly bacteria, algae, and macro-invertebrates) under such acidic conditions, and their trophic interactions, their potential impact on the ecosystem functioning was poorly investigated. The present study aimed to assess the influence of chironomid larvae on oxygen dynamics and iron cycle in the sediment of acidic pit lakes. In the Mining Lake 111, used as a study case since 1996, Chironomus crassimanus (Insecta, Diptera) is the dominant benthic macro-invertebrate species and occurs at relatively high abundances in shallow water. A 16-day laboratory experiment using microcosms combined with high resolution measurements (DET gel probes and O2 microsensors) was carried out. The burrowing activity of C. crassimanus larvae induced a 3-fold increase of the diffusive oxygen uptake by sediment, indicating a stimulation of the mineralization of organic matter in the upper layers of the sediment. The iron cycle was also impacted (e.g. lower rates of reduction and oxidation, increase of iron-oxidizing bacteria abundance, stimulation of mineral formation) but with no significant effect on the iron flux at the sediment-water interface, and thus on the water acidity budget. This work provides the first assessment of bioturbation in an acidic mining lake and shows that its influence on biogeochemistry cannot be neglected.

Aquatic Geochemistry, 2011

A geochemical model was incorporated into a stratification model for lakes to create the model pa... more A geochemical model was incorporated into a stratification model for lakes to create the model package: DYCD-CORE, a numerical code that couples the thermal and hydrodynamic capabilities of DYRESM and the geochemical capabilities of the reactive transport model CORE2D V4. Based on the chemical composition of solutes calculated in each node for each time step, density was computed using specific partial molal volumes of all considered solutes and fed back into the stratification module of the program package. The density calculated each time step leads to a strong coupling of hydrodynamics and hydrogeochemistry and reflects the complex interaction as it is present in all lakes. To demonstrate the functionality of the numerical approach, an example of an iron-meromictic lake was chosen, where the reactivity of the dissolved iron kept the water body perennially stratified. To critically validate the model results, temperatures were continously measured at high vertical and temporal resolution in a field investigation of Waldsee (near Döbern, Germany). Multiparameterprobe profiles and water samples confirmed the continous chemical stratification and served as initial and boundary conditions for the simulation period. The model package DYCD-CORE could reproduce the permanent stratification as it were in the lake. A demonstration run using the standard UNESCO equation for density, and hence assuming non-reactive solutes, failed entirely. Hence, stratification models using salinity for density are not suited for simulating density created by lake-internal geochemical transformation of solutes. However, density can be based directly on the simultaneous numerical simulation of lake geochemistry. Predictive modeling of changing lake circulation in a variable climate or considering change of use will require a proper inclusion of the geochemistry as demonstrated in this paper.

Pit lakes are known for their tendency to become meromictic. Biogeochemical reactions are one pot... more Pit lakes are known for their tendency to become meromictic. Biogeochemical reactions are one potential reason. In these cases, lake hydrodynamics is controlled by lake water biogeochemistry. Most of the existing numerical stratification models for lakes calculate the chemical composition separately from hydrodynamic and transport calculations. However, if the geochemistry controls the stability of the stratification, temperature profiles cannot be predicted accurately without considering geochemical transformations in the hydrodynamic model.

era un chica que nació con un gusto a la naturaleza y a su corta edad le nació una intriga hacia ... more era un chica que nació con un gusto a la naturaleza y a su corta edad le nació una intriga hacia las serpientes, porque su papa le gustaban las serpientes y las investigaba, la niña fue creciendo y su conocimiento e intriga sobre las serpientes fue avanzando. Halos pocos años su padre falleció y dejo en marcha un proyecto el cual era asegurarse de la existencia de una nueva especie de serpiente situada en el más profundo de las montañas del Ecuador. Tres días después de su muerte ella le propuso concluir el proyecto de su padre, dos años después ella emprendió la expedición en la búsqueda de esa nueva especie de serpiente. Ella comenzó a introducirse en lo más profundo de estas montañas y cada día se emocionaba más porque encontraba muchas variedades de serpientes. Días después ella llego a un lugar muy alejado de la civilización Karla no miraba ni un animal y personas cercas ella estaba completamente perdida en esta montaña .un año después un pequeño grupo de personas integrado por 4 personas despareció en extrañas circunstancias en la misma montaña que se perdió Karla este grupo estaba en una búsqueda biológica-natural .este grupo estaba integrado por gloria Martínez una escritora bogotana. Martha ríos un biológica natural. Juan zapata y Jonathan correa dos hermanos ex militares. Gloria antes de su desaparición tenía la costumbre de copiar absolutamente todo lo que había pasado en el día en un grueso diario con pasta de cartón y hojas bond de fina y suave, textura.