Santiago del Estero, Argentina
Santiago del Estero, Argentina

The National University of Santiago del Estero is an Argentine national university located in the capital of Santiago del Estero Province. Its 1973 establishment gathered the existing Tucumán University school of agronomy and the Córdoba University forestry institute , as well as new schools created for the purpose. Wikipedia.

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Nazareno M.A.,National University of Santiago del Estero
LWT - Food Science and Technology | Year: 2011

Flavonoids and ascorbic acid are antioxidants usually consumed together in foods, taking this into account, the antiradical capacity of mixtures of ascorbic acid with some representative flavonoids (flavanones, chalcones and flavonols) against the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH. ) was evaluated. Antiradical capacities of naringin, naringenin, hesperidin, hesperetin, naringin chalcone, naringin dihydrochalcone, rutin and quercetin were measured alone and in different combinations with ascorbic acid. Experimental and theoretical values of antiradical activities for these mixtures as well as the values obtained in sequential reactions were compared in order to determine synergistic or antagonistic effects. Among the different ascorbic acid-flavonoid combinations analyzed only the mixture with naringin or quercetin exhibited synergistic effects, the mixture activity being 33 and 18% higher than the theoretical value, respectively. On the contrary, antagonistic effects were found in the cases of rutin, hesperidin, naringin chalcone, naringin dihydrochalcone and naringenin. Moreover, only hesperetin showed an additive effect. These behaviours were ascribed to the regeneration of the oxidized species on the basis of the structural features of each flavonoid and their different reactivity against DPPH. These results show that the antiradical activity can be modified by the interaction among the mixture constituents and this may be considered to improve antioxidant formulations. © 2010 Elsevier Ltd.

Valle L.,National University of Santiago del Estero | Moran Vieyra F.E.,National University of Santiago del Estero | Borsarelli C.D.,National University of Santiago del Estero
Photochemical and Photobiological Sciences | Year: 2012

The singlet and triplet excited states properties of lumiflavin (LF), riboflavin (RF), flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) in reversed micelles (RM) of sodium docusate (AOT) in n-hexane solutions were evaluated as a function of the water to surfactant molar ratio, w0 = [H2O]/[AOT], by both steady-state and time-resolved absorption and fluorescence spectroscopy. The results indicated that hydrogen-bonding interactions between the isoalloxazine ring of the flavins with the water molecules of the micellar interior play a crucial role on the modulation of the excited state properties of the flavins. Fluorescence dynamic experiments in the RM, allowed the calculation of similar values for both the internal rotational time of the flavins (θi) and the hydrogen-bonding relaxation time (τHB), e.g. ≈ 7 and 1.5 ns at w0 = 1 and 20, respectively. In turn, the triplet state lifetimes of the flavins were also enlarged in RM solutions at low w0, without modifications of their quantum yields. A hydrogen bonding relaxation model is proposed to explain the singlet excited state properties of the flavins, while the changes of the triplet state decays of the flavins were related with the global composition and strength of the hydrogen bonding network inside of the RM. © The Royal Society of Chemistry and Owner Societies.

Disalvo E.A.,National University of Santiago del Estero | Bouchet A.M.,National University of Santiago del Estero | Frias M.A.,National University of Santiago del Estero
Biochimica et Biophysica Acta - Biomembranes | Year: 2013

Analysis of the band corresponding to the frequency of vibrational symmetric stretching mode of methylene groups in the lipid acyl chains and the bands of water below and above the phase transition of different lipids by Fourier transform infrared spectroscopy gives strong support to the formation of confined water pockets in between the lipid acyl chains. Our measures and analysis consolidate the mechanism early proposed by Traüble, in the sense that water is present in kinks formed by trans-gauche isomers along the hydrocarbon tails. The formation of these regions depends on the acyl lipid composition, which determines the presence of different populations of water species, characterized by its degree of H bond coordination in fluid saturated or unsaturated lipids. The free energy excess due to the reinforcement of the water structure along few water molecules in the adjacencies of exposed membrane residues near the phase transition is a reasonable base to explain the insertion and translocation of polar peptides and aminoacid residues through the biomembrane on thermodynamic and structural grounds. © 2013 Published by Elsevier B.V.

Disalvo E.A.,National University of Santiago del Estero | Bouchet A.M.,National University of Santiago del Estero
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

Zeta potential determinations obtained from liposome electrophoretic mobilties provide direct evidence of the Arg orientation in the lipid interphase of phosphatidylcholine and phosphatidilethanolamine bilayers. In addition, the zeta potential of liposomes has also been used to determine the variations of the degree of coverage (θ) of individual liposomes of different lipids and to calculate the dissociation constants and the stoichiometry of the binding.The adsorption of positively charged aminoacids to these membranes deviates from a Langmuir type isotherm with the progressive demethylation of the phosphatidylcholine group suggesting that the adsorption takes place in non independent sites, probably producing surface rearrangements.The cooperative effect observed in dimirystoylphosphatidilethanolamines but not in phosphatidylcholines seems to be related to a reorganization of interfacial water as confirmed by fluorescence spectroscopy using Laurdan as an interphacial probe.It is concluded that that zeta potential measurements provide direct evidence of aminoacid orientation in a lipid interphase giving consistency of the findings suggested by MD and surface spectroscopic studies, congruent with the proposal that the guanidine group is buried in the membrane in a water environment. © 2012 Elsevier B.V.

Costaguta R.,National University of Santiago del Estero
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2015

Computer Supported Collaborative Learning (CSCL) is an emerging interdisciplinary research area that deals with the formation of students groups to work and to learn together in an educational context. One of the factors that affect successful collaborative learning is the group composition. This paper surveys the most relevant researches carried out in this field to date. For each one it describes the applied criterion to form learning groups and the way in which the grouping criterion is applied. These researches are compared and some conclusions are outlined. © Springer International Publishing Switzerland 2015.

Zanini V.P.,National University of Santiago del Estero | Lopez De Mishima B.,National University of Santiago del Estero | Solis V.,National University of Cordoba
Sensors and Actuators, B: Chemical | Year: 2011

A biosensor based on the immobilization of lactate oxidase (LOx) on a glassy carbon electrode modified with laponite/chitosan hydrogels for the quantification of l-lactate in alcoholic beverages and dairy products is presented. Ferrocene-methanol (FcMe) is used as artificial mediator. The purpose of this work is to determine the best hydrogel composition from the analytical point of view. The characterization of the hydrogels was carried out by CV, amperometry and EIS. According to permeabilities and charge transfer resistances for ferrocyanide (used as molecular probe) as well as the enzymatic behavior of the enzyme for l-lactate, the best laponite/chitosan mass ratio found was 25/50. The distinct features of the bioelectrode are its long stability, its ability to reject or minimize most interferents including ascorbic acid, and its excellent analytical response, which allowed the reduction of the enzyme content below 0.5 U, for a sensitivity of (0.326 ± 0.003) A cm -2 M-1, with a time response lower than 5 s and a detection limit of (3.8 ± 0.2) × 10-6 M. Our l-lactate biosensor was validated by comparison with a standard spectroscopic method. © 2011 Elsevier B.V.

Bravo S.,National University of Santiago del Estero
IAWA Journal | Year: 2010

This study examined anatomical responses to fire damage of the cambium in Schinopsis lorentzii and Aspidosperma quebracho-bianco. Bole cross sections were extracted from specimens with external signs of fire damage. Samples were taken from zones designated normal, discoloured and wound altered. The vessel, fibre, axial and ray parenchyma percentages, tangential vessel diameter, vessels per mm2, rays per mm, and ray width and height of these zones were compared. Fire scars and fire marks were identified on cross sections of S. lorentzii and A. quebracho-bianco. The fire marks reflect minor wounds that did not affect wood formation. The fire scars, on the other hand, are the result of wounds that interrupted cambial activity thus affecting the shape of the bole and causing discolouration of pre-existing wood adjacent to wounds. The wood formed after fire damage included callus, barrier zones at fire scar edges and the formation of ribs of wound wood. The wound altered zone was characterised by a decrease in the percentage of vessels and fibres, an increase in the percentage of axial parenchyma, the formation of grouped rays, a decrease in vessel tangential diameter, and occurrence of fibres with atypical structure. Disorientation in the axial xylem system was observed in the barrier zone. The anatomical responses to cambium damage and formation of discoloured wood and woundwood ribs suggest that wood quality and utilisable volume of bole in the studied species is affected by fire.

Disalvo E.A.,National University of Santiago del Estero | Frias M.A.,National University of Santiago del Estero
Langmuir | Year: 2013

It has been suggested that water in confined regions presents different properties than bulk water, mainly because of the changes in water population species that may be induced by the adjacent walls of different polarities in terms of hydrogen bond formation. In this context, it would be expected that lipids in the gel and the fluid states should offer different templates for water organization. The presence of water pockets or defects in lipid bilayers has been proposed to explain the insertion of charged and polar peptides and amino acids in membranes. In this work, we provide direct evidence by means of FTIR spectroscopy that water band profiles are changed whether lipids are in the solid state, in the gel state after heating and cooling across the phase transition, or in the fluid state. The different bands found in each case were assigned to different H-bonded water populations in agreement with the exposure of carbonyl groups. © 2013 American Chemical Society.

Nazareno M.A.,National University of Santiago del Estero
Acta Horticulturae | Year: 2013

A review of the latest world-wide findings from scientific studies about the medicinal properties of cactus products is presented as well as their traditional and popular uses. Plants were used by ancient civilizations to cure diseases and heal wounds for thousands of years. Cactus cladodes, fruits, and flowers have been traditionally used as medicines in several countries. Cladodes are still used in folk medicine for the treatment of gastric ulcer and for its healing activity as therapeutic agents. The properties of the infusions of cactus dried flowers to prevent prostate cancer are also well-known. Remarkable progress has been made over the past decades in disease prevention considering fruit, vegetables and herbs. Recent scientific investigations confirmed that cactus products may be efficiently used as a source of phytochemicals, such as mucilage, fibres, pigments and antioxidants. Scientific studies in experimental models confirmed that lyophilized cladodes have significant anti-ulcer effect, protective effect against gastric lesions as well as antiinflammatory activity. Diet supplementation with cactus pear fruits in healthy human has shown to decrease the oxidative stress, and, therefore, improves their overall antioxidant status. Cactus pear fruits have also been studied as ovariancancer preventive. Their ability in suppressing carcinogenesis of in vitro and in vivo models has been assessed. Opuntia ficus-indica cladodes were supplied to hypercholesterolemic rats and a marked decrease in cholesterol and triglycerides levels was found in plasma samples. Experiments in diabetes mellitus non-insulindependent patients have confirmed the hypoglycemic effects of Opuntia streptacantha cladodes. Moreover, consumption of cactus young cladodes has shown to reduce obesity and blood glucose. Experiments concerning the antiviral action of cactus cladode extracts have been conducted against viruses such as herpes, HIV-1 virus and influenza A. Functional properties of cactus products can be exploited more efficiently in the food, cosmetic, and pharmaceutical industries if research is encouraged.

Arrua D.,National University of Santiago del Estero | Strumia M.C.,National University of Cordoba | Nazareno M.A.,National University of Santiago del Estero
Journal of Agricultural and Food Chemistry | Year: 2010

The immobilization of caffeic acid (CA) on a polypropylene (PP) film was successfully performed through the covalent binding of the caffeoyl chloride on a modified polymeric surface of PP films grafted with hydroxyethyl methacrylate as monomer (PP-g-HEMA). The different reaction steps were monitored by FT-IR spectroscopy. The synthesized films were characterized by Folin- Ciocalteu method by measuring the available phenolic groups as caffeic acid equivalents linked to the surface. The antioxidant efficiency of the modified polymers was evaluated by typical spectrophometric methods, such as the bleaching of radicals DPPH· and ABTS·+, and the inhibition of the enzymatically induced coupled oxidation of linoleic acid and betacarotene. The available phenolic groups on the modified film presented a good correlation with the antiradical activity toward DPPH·. Moreover, the polymer synthesized in this work showed a good protective activity against ascorbic acid oxidation in real samples of orange juice. ©2010 American Chemical Society.

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