Estudio teórico - experimental del mecanismo de reacción de sustratos aromáticos fluorados con nucleófilos nitrogenados

Fil:Mac Cormack, Patricio Guillermo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Scaling laws of quiet-Sun coronal loops

We study a series of relations between physical parameters in coronal loops of the quiet Sun reconstructed by combining tomographic techniques and modeling of the coronal magnetic field. We use differential emission measure tomography (DEMT) to determine the three-dimensional distribution of the electron density and temperature in the corona, and we model the magnetic field with a potential-field source-surface (PFSS) extrapolation of a synoptic magnetogram. By tracing the DEMT products along the extrapolated magnetic field lines, we obtain loop-averaged electron density and temperature. Also, loop-integrated energy-related quantities are computed for each closed magnetic field line. We apply the procedure to Carrington rotation 2082, during the activity minimum between Solar Cycles 23 and 24, using data from the Extreme Ultraviolet Imager on board the Solar Terrestrial Relations Observatory (STEREO) spacecraft. We find a scaling law between the loop-average density N and loop length L,Nm∼L-0.35, but we do not find a significant relation between loop-average temperature and loop length. We confirm though the previously found result that loop-average temperatures at the equatorial latitudes are lower than at higher latitudes. We associate this behavior with the presence at the equatorial latitudes of loops with decreasing temperatures along their length (“down” loops), which are in general colder than loops with increasing temperatures (“up” loops). We also discuss the role of “down” loops in the obtained scaling laws of heating flux versus loop length for different heliographic latitudes. We find that the obtained scalings for quiet-Sun loops do not generally agree with those found in the case of AR loops from previous observational and theoretical studies. We suggest that to better understand the relations found, it is necessary to forward model the reconstructed loops using hydrodynamic codes working under the physical conditions of the quiet-Sun corona.Fil: Mac Cormack, Cecilia. Universidad Nacional de Tres de Febrero; Argentina. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Lopez Fuentes, Marcelo Claudio. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Mandrini, Cristina Hemilse. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Lloveras, Diego Gustavo. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Poisson, Mariano. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina. Universidad Nacional de Tres de Febrero; ArgentinaFil: Vasquez, Alberto Marcos. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina. Universidad Nacional de Tres de Febrero; Argentin

Extracellular hydrolytic enzyme production by proteolytic bacteria from the Antarctic

Cold−adapted marine bacteria producing extracellular hydrolytic enzymes are important for their industrial application and play a key role in degradation of particulate organic matter in their natural environment. In this work, members of a previously−obtained protease−producing bacterial collection isolated from different marine sources from Potter Cove (King George Island, South Shetlands) were taxonomically identified and screened for their ability to produce other economically relevant enzymes. Eighty−eight proteolytic bacterial isolates were grouped into 25 phylotypes based on their Amplified Ribosomal DNA Restriction Analysis profiles. The sequencing of the 16S rRNA genes from representative isolates of the phylotypes showed that the predominant culturable protease−producing bacteria belonged to the class Gammaproteobacteria and were affiliated to the genera Pseudomonas, Shewanella, Colwellia, and Pseudoalteromonas, the latter being the predominant group (64% of isolates). In addition, members of the classes Actinobacteria, Bacilli and Flavobacteria were found. Among the 88 isolates screened we detected producers of amylases (21), pectinases (67), cellulases (53), CM−cellulases (68), xylanases (55) and agarases (57). More than 85% of the isolates showed at least one of the extracellular enzymatic activities tested, with some of them producing up to six extracellular enzymes. Our results confirmed that using selective conditions to isolate producers of one extracellular enzyme activity increases the probability of recovering bacteria that will also produce additional extracellular enzymes. This finding establishes a starting point for future programs oriented to the prospecting for biomolecules in Antarctica.Fil: Tropeano, Mauro. Biosidus; ArgentinaFil: Vazquez, Susana Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Coria, Silvia. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Turjanski, Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Cicero, Daniel. Fundación Instituto Leloir; Argentina. University of Rome “Tor Vergata”. Department of Chemical Science and Technology; ItaliaFil: Bercovich, Andrés. Biosidus; ArgentinaFil: Cormack, Mac. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentin

The Magnetic Environment of a Stealth Coronal Mass Ejection

Interest in stealth coronal mass ejections (CMEs) is increasing due to their relatively high occurrence rate and space weather impact. However, typical CME signatures such as extreme-ultraviolet dimmings and post-eruptive arcades are hard to identify and require extensive image processing techniques. These weak observational signatures mean that little is currently understood about the physics of these events. We present an extensive study of the magnetic field configuration in which the stealth CME of 2011 March 3 occurred. Three distinct episodes of flare ribbon formation are observed in the stealth CME source active region (AR). Two occurred prior to the eruption and suggest the occurrence of magnetic reconnection that builds the structure that will become eruptive. The third occurs in a time close to the eruption of a cavity that is observed in STEREO-B 171 Å data; this subsequently becomes part of the propagating CME observed in coronagraph data. We use both local (Cartesian) and global (spherical) models of the coronal magnetic field, which are complemented and verified by the observational analysis. We find evidence of a coronal null point, with field lines computed from its neighborhood connecting the stealth CME source region to two ARs in the northern hemisphere. We conclude that reconnection at the null point aids the eruption of the stealth CME by removing the field that acted to stabilize the preeruptive structure. This stealth CME, despite its weak signatures, has the main characteristics of other CMEs, and its eruption is driven by similar mechanisms

Three-Dimensional Reconstruction and Thermal Modeling of Observed Loops

Due to their characteristic temperature and density, loop structures in active regions (ARs) can be seen bright in extreme ultraviolet (EUV) and soft X-ray images. The semiempirical determination of the three-dimensional (3D) distribution of basic physical parameters (electronic density and temperature, and magnetic field) is a key constraint for coronal heating models. In this work we develop a technique for the study of EUV bright loops based on differential emission measure (DEM) analysis and we first apply it to AR structures observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The 3D structure and intensity of the magnetic field of the observed EUV loops are modeled using force-free field extrapolations based on magnetograms taken by the Helioseismic and Magnetic Imager (HMI) on board SDO. In this work we report the results obtained for several bright loops identified in different ARs. Our analysis indicates that the mean and width of the temperature distributions are nearly invariant along the loop lengths. For a particular loop we study its temporal evolution and find that these characteristics remain approximately constant for most of its life time. The appearance and disappearance of this loop occurs at time-scales much shorter than its life time of ≈ 2.5 hours. The results of this analysis are compared with numerical simulations using the zero-dimensional (0D) hydrodynamic model, Enthalpy-Based Thermal Evolution of Loops (EBTEL). We study two alternative heating scenarios: first, we apply a constant heating rate assuming loops in quasi-static equilibrium, and second, we heat the loops using impulsive events or nanoflares. We find that all the observed loops are overdense with respect to a quasi-static equilibrium solution and that the nanoflare heating better reproduces the observed densities and temperatures.Fil: Nuevo, Federico Alberto. Universidad de Buenos Aires. Ciclo Básico Común; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Mac Cormack, Cecilia. Universidad Nacional de Tres de Febrero. Departamento de Ciencia y Tecnologia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Lopez Fuentes, Marcelo Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Vasquez, Alberto Marcos. Universidad Nacional de Tres de Febrero. Departamento de Ciencia y Tecnologia.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Mandrini, Cristina Hemilse. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Characteristics of a Cold-Adapted L-glutaminase with Potential Applications in the Food Industry

L-glutaminases are enzymes that catalyze the hydrolysis of L-glutamine, producing L-glutamate and ammonium, and they have promising applications in pharmaceutical and food industries. Several investigations have focused on thermo-tolerant L-glutaminases; however, studies on cold-adapted L-glutaminases have not been reported. These enzymes could be useful in the food industry because they display high catalytic activity at low and room temperatures, a valuable feature in processes aimed to save energy. Besides, they can be easily inactivated by warming and are suitable to prevent decomposition of thermo-labile compounds. The objectives of this work were to characterize the L-glutaminase from the Antarctic bacterium Bizionia argentinensis and analyze its capability as flavor enhancer of protein hydrolysates. The enzyme was heterologously expressed and purified from Escherichia coli, obtaining optimum and homogeneous yields. Kinetic parameters Km and Vmax were located at the lower and upper range of values reported for L-glutaminases, suggesting high catalytic efficiency. Optimum temperature was 25 °C, and the enzyme conserved around 90% of maximum activity at 0 °C and in presence of 15% (v/v) ethanol and methanol. In saline conditions, the enzyme conserved around 80% of maximum activity in 3 M NaCl. Analysis of structural model suggested cold-adaptation features such as low Arg/(Arg+Lys) ratio and fewer intramolecular interactions than mesophilic and thermo-tolerant L-glutaminases. This work provides a novel cold-adapted L-glutaminase with promising features in the food industry.Fil: Ferreira, Flavia Vanina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Entre Ríos. Universidad Nacional de Entre Ríos. Centro de Investigaciones y Transferencia de Entre Ríos; ArgentinaFil: Herrmann Andrade, Andreina M.. Universidad Nacional de Entre Rios. Facultad de Cs. de la Alimentación. Departamento de Cs. de Los Alimentos; ArgentinaFil: Binolfi, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Calabrese, Carla D.. Universidad Nacional de Entre Rios. Facultad de Cs. de la Alimentación. Departamento de Cs. de Los Alimentos; ArgentinaFil: Mac Cormack, Walter Patricio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Musumeci, Matias Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Entre Ríos. Universidad Nacional de Entre Ríos. Centro de Investigaciones y Transferencia de Entre Ríos; Argentin

Bioremediation of hydrocarbon-contaminated soil from Carlini Station, Antarctica: effectiveness of different nutrient sources as biostimulation agents

Logistics and scientific activities carried out in Antarctic stations entail the risk of contamination by fuels. Among remediation strategies, biostimulation significantly improves the efficiency of hydrocarbons (HCs) removal. A 1-year-long field trial was performed in mesocosms filled with soil chronically contaminated with HCs. Three nutrient sources were evaluated as biostimulation agents: inorganic salts (with and without aeration by mixing), a slow-release granular fertilizer (Nitrofoska®) and a commercial bioremediation product (OSEII®). Their performance was assessed considering the number of culturable bacteria, the changes induced in the structure of bacterial communities, the HCs removal efficiencies and the estimation of the abiotic and biodegradative losses of HCs. The soil indigenous microbiota reduced the concentration of hydrocarbons by up to 50% in 50 days and 87% in 365 days depending on the biostimulation agent used. OSEII® (a mixture of surfactants, nutrients, and enzymes) performed better in the medium term, promoting bacterial growth and rapidly inducing changes in the structure of bacterial community, and Nitrofoska® proved to be more efficient for long-term processes, less affecting the size and structure of the microbiota. A mixed strategy combining the fastest action of commercial products acting during summer with slow-release fertilizers acting throughout the year is proposed as a long-term bioremediation treatment for Antarctic areas where the temperature rises above the freezing point and the ground is free of snow shortly during summer. This study highlights the importance of conducting research to develop remediation processes compatible with the Antarctic Treaty, exploiting the metabolic potential of the indigenous microbiota.Fil: Villalba Primitz, Julia Elena Rosina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Vázquez, Susana Claudia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Microbiología Industrial y Biotecnología; ArgentinaFil: Ruberto, Lucas Adolfo Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Lo Balbo, Alfredo. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Mac Cormack, Walter Patricio. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentin

Studies toward the comprehension of fungal-macroalgae interaction in cold marine regions from a biotechnological perspective

In marine ecosystems, macroalgae are the habitat for several microorganisms, fungi being among them. In the Antarctic benthic coastal ecosystem, macroalgae play a key role in organic matter cycling. In this study, 13 different macroalgae from Potter Cove and surrounding areas were sampled and 48 fungal isolates were obtained from six species, four Rhodophyta Ballia callitricha, Gigartina skottsbergii, Neuroglossum delesseriae and Palmaria decipiens, and two Phaeophyceae: Adenocystis utricularis and Ascoseira mirabilis. Fungal isolates mostly belonged to the Ascomycota phylum (Antarctomyces, Cadophora, Cladosporium, Penicillium, Phialocephala, and Pseudogymnoascus) and only one to the phylum Mucoromycota. Two of the isolates could not be identified to genus level, implying that Antarctica is a source of probable novel fungal taxa with enormous bioprospecting and biotechnological potential. 73% of the fungal isolates were moderate eurypsychrophilic (they grew at 5–25 °C), 12.5% were eurypsychrophilic and grew in the whole range, 12.5% of the isolates were narrow eurypsychrophilic (growth at 15–25 °C), and Mucoromycota AUe4 was classified as stenopsychrophilic as it grew at 5–15 °C. Organic extracts of seven macroalgae from which no fungal growth was obtained (three red algae Georgiella confluens, Gymnogongrus turquetii, Plocamium cartlagineum, and four brown algae Desmarestia anceps, D. Antarctica, Desmarestia menziesii, Himantothallus grandifolius) were tested against representative fungi of the genera isolated in this work. All extracts presented fungal inhibition, those from Plocamium cartilagineum and G. turquetii showed the best results, and for most of these macroalgae, this represents the first report of antifungal activity and constitute a promising source of compounds for future evaluation.Fil: Martorell, M.M.. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Microbiología, Inmunología y Biotecnología. Cátedra de Microbiología Industrial y Biotecnología; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Lannert, Micaela. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Matula, Carolina Veronica. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Quartino, Maria Liliana. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: de Figueroa, L.I.C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Planta Piloto de Procesos Industriales Microbiológicos; Argentina. Universidad Nacional de Tucumán; ArgentinaFil: Mac Cormack, Walter Patricio. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Ruberto, Lucas Adolfo Mauro. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentin