Combined Experimental and Molecular Simulation Study of Insulin-Chitosan Complexation Driven by Electrostatic Interactions

Protein−polysaccharide complexes constructed via self-assembly methods are often used to develop novel 17 biomaterials for a wide range of applications in biomedicine, food, and biotechnology. The objective of this work was to 18 investigate theoretically and to demonstrate via constant-pH Monte Carlo simulations that the complexation phenomenon 19 between insulin (INS) and the cationic polyelectrolyte chitosan (CS) is mainly driven by an electrostatic mechanism. 20 Experimental results obtained from FTIR spectra and ζ-potential determinations allowed us to complement the conclusions. 21 The characteristic absorption bands for the complexes could be assigned to a combination of signals from CS amide I and INS 22 amide II. The second peak corresponds to the interaction between the polymer and the protein at the level of amide II. INS− 23 CS complexation processes not expected when INS is in its monomeric form, but for both tetrameric and hexameric forms, 24 incipient complexation due to charge regulation mechanism took place at pH 5. The complexation range was observed to be 5.5 25 < pH < 6.5. In general, when the number of INS units increases in the simulation process, the solution pH at which the 26 complexation can occur shifts toward acidic conditions. CS’s chain interacts more efficiently, i.e. in a wider pH range, with INS 27 aggregates formed by the highest monomer number. The charge regulation mechanism can be considered as a previous phase 28 toward complexation (incipient complexation) caused by weak interactions of a Coulombic nature.Fil: Prudkin Silva, Cecilia Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Pérez, Carlos E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Martínez, Karina Dafne. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Químicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Químicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Barroso da silva, Fernando. Universidade do Sao Paulo. Departamento de Bioquímica; Brasi

Combined Experimental and Molecular Simulation Study of Insulin-Chitosan Complexation Driven by Electrostatic Interactions

Protein−polysaccharide complexes constructed via self-assembly methods are often used to develop novel 17 biomaterials for a wide range of applications in biomedicine, food, and biotechnology. The objective of this work was to 18 investigate theoretically and to demonstrate via constant-pH Monte Carlo simulations that the complexation phenomenon 19 between insulin (INS) and the cationic polyelectrolyte chitosan (CS) is mainly driven by an electrostatic mechanism. 20 Experimental results obtained from FTIR spectra and ζ-potential determinations allowed us to complement the conclusions. 21 The characteristic absorption bands for the complexes could be assigned to a combination of signals from CS amide I and INS 22 amide II. The second peak corresponds to the interaction between the polymer and the protein at the level of amide II. INS− 23 CS complexation processes not expected when INS is in its monomeric form, but for both tetrameric and hexameric forms, 24 incipient complexation due to charge regulation mechanism took place at pH 5. The complexation range was observed to be 5.5 25 < pH < 6.5. In general, when the number of INS units increases in the simulation process, the solution pH at which the 26 complexation can occur shifts toward acidic conditions. CS’s chain interacts more efficiently, i.e. in a wider pH range, with INS 27 aggregates formed by the highest monomer number. The charge regulation mechanism can be considered as a previous phase 28 toward complexation (incipient complexation) caused by weak interactions of a Coulombic nature.Fil: Prudkin Silva, Cecilia Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Pérez, Carlos E.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Martínez, Karina Dafne. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Industrias. Instituto de Tecnología de Alimentos y Procesos Químicos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Tecnología de Alimentos y Procesos Químicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Tecnología en Polímeros y Nanotecnología. Universidad de Buenos Aires. Facultad de Ingeniería. Instituto de Tecnología en Polímeros y Nanotecnología; ArgentinaFil: Barroso da silva, Fernando. Universidade do Sao Paulo. Departamento de Bioquímica; Brasi

Synthesis and Structural Analysis of Push-Pull Imidazole-Triazole Based Fluorescent Bifunctional Chemosensor for CU2+ and FE2+ Detection

[Abstract] Fluorescent imidazole-triazole based ligands L1 and L2 have been designed as chemical push-pull chemosensors for divalent metal ions and synthesized through palladium-catalyzed cross-coupling reactions using indium organometallics and click chemistry. The novel ligands exhibit intense absorption in the ultraviolet region with high molar extinction coefficients, and strong fluorescence emission with large Stokes displacements. On the basis of UV–Vis absorption spectroscopy and fluorescence emission data in acetonitrile, L1 is shown as a bifuncional chemosensor with differential response for Fe2+ and Cu2+ over a range of selected 3d divalent and other metal ions. The binding site of the ligand was established by single-crystal X-ray diffraction and 1H NMR spectroscopy studies. The association constants, determined by spectrofluorimetric titrations, show a steady binding affinity of L1 for Cu2+ and Fe2+ in comparison with other previously reported fluorescent bidentate chemosensors, offering the lowest limit of detection (LOD) with Cu2+. DFT calculations provide a rationale properly understanding and interpreting the experimentally observed results. Indeed, a mechanism of the different optical responses of L1 towards 3d divalent metal ions is proposed.We thank the Spanish Ministerio de Ciencia, Innovación y Universidades (PGC2018-097792-B-I00), Xunta de Galicia (GRC2018/039 and ED431B 2020/52) and EDRF funds for financial and human support. ADL thanks the Xunta de Galicia for a predoctoral fellowship (EDA 481A-2020/017). LV thanks CACTI for X-ray measurementsXunta de Galicia; GRC2018/039Xunta de Galicia; ED431B 2020/52Xunta de Galicia; ED 481A-2020/01

Classical field theory on Lie algebroids: Variational aspects

The variational formalism for classical field theories is extended to the setting of Lie algebroids. Given a Lagrangian function we study the problem of finding critical points of the action functional when we restrict the fields to be morphisms of Lie algebroids. In addition to the standard case, our formalism includes as particular examples the case of systems with symmetry (covariant Euler-Poincare and Lagrange Poincare cases), Sigma models or Chern-Simons theories.Comment: Talk deliverd at the 9th International Conference on Differential Geometry and its Applications, Prague, September 2004. References adde

In Vitro Digestion Assays Using Dynamic Models for Essential Minerals in Brazilian Goat Cheeses

Goat cheeses have important nutritional properties, with an emphasis on proteins, lipids (high digestibility), and essential minerals. This study analyzes the bioavailability of Ca, Mg, and Zn in Brazilian cheeses using an in vitro dynamic digestion method. Two self-produced fresh cheeses, cow and goat Minas frescal cheese, and two commercial matured goat cheeses, Blue and Pyramid, were analyzed. Brazilian goat cheeses are potential sources of essential minerals (Ca, Mg, and Zn). Variations of 103–598 mg/100 g for Ca, 13.62–41.64 mg/100 g for Mg, and 9.79–13.23 mg/100 g for Zn were observed in the studied samples. The pH concentration, enzyme performance, and protein and lipid content of Brazilian cheeses affected the solubility of essential minerals in the intestinal fraction. The percentages of minerals found in the permeate stream, equivalent to absorption of Ca and Zn, were lower in Minas frescal goat cheese than Minas frescal cow cheese, whereas that of Mg was higher. Pyramid and Minas frescal goat cheeses had the higher values of Mg and Zn bioavailability, respectively. This study supports, for the first time, the usefulness of the dynamic simulation of the human gastrointestinal tract for the study of mineral bioavailability in cheeses.The authors would like to thank the São Paulo Research Foundation (FAPESP) for the scholarship grant of PhD student José Teixeira, and for the research internship abroad (regular scholarship n° 2018/08864–8 and BEPE—n° 2019/13600–2). Juliana Azevedo Lima Pallone would like to thank the financial support of Brazil (FAPESP 2018/09759–3). The Coordination for the Improvement of Higher Education Personnel (CAPES) (Financial Code 001)

La Pedagogía de la diversidad. Perspectivas actuales

Al siglo XXI han llegado, también, movimientos de ideas, que no se han convertido en tendencias, y que se unen a las que se han mencionado anteriormente como: el constructivismo (de diferentes, matices), el holismo ambientalista, el pensamiento complejo, la pedagogía crítica (con sus variantes) y la llamada pedagogía de la diversidad, entre otras polémicas, que ofrecemos en este estudio para su análisis crítico por la comunidad pedagógica nacional e internacional. Para enfrentar el mismo se han utilizado con conjunto de métodos de las investigaciones macrosociales y microsociales con énfasis en las cualitativas, favorecidas desde sus procedimientos metodológicos y la indagación científica. En el estudio se reflexiona sobre el papel de la Pedagogía de la diversidad como elemento aglutinador de la Inclusión educativa para enfrentar los cambios que se avecinan en la formación de los profesionales que requiere el siglo XXI

Prevalence and Diagnosis of Latent Tuberculosis Infection in Young Children in the Absence of a Gold Standard

Introduction For adequate disease control the World Health Organization has proposed the diagnosis and treatment of latent tuberculous infection (LTBI) in groups of risk of developing the disease such as children. There is no gold standard (GS) test for the diagnosis of LTBI. The objective of this study was to estimate the prevalence of LTBI in young children in contact with a household case of tuberculosis (TB-HCC) and determine the accuracy and precision of the Tuberculin Skin Test (TST) and QuantiFERON-TB Gold in-tube (QFT) used in the absence of a GS. Methods We conducted a cross-sectional study in children up to 6 years of age in Manaus/Brazil during the years 2009-2010. All the children had been vaccinated with the BCG and were classified into two groups according to the presence of a TB-HCC or no known contact with tuberculosis (TB). The variables studied were: the TST and QFT results and the intensity and length of exposure to the index tuberculosis case. We used the latent class model to determine the prevalence of LTBI and the accuracy of the tests. Results Fifty percent of the children with TB-HCC had LTBI, with the prevalence depending on the intensity and length of exposure to the index case. The sensitivity and specificity of TST were 73% [95% confidence interval (CI): 53-91] and 97% (95%CI: 89-100), respectively, versus 53% (95%CI: 41-66) and 81% (95%CI:71-90) for QFT. The positive predictive value of TST in children with TB-HCC was 91% (95%CI: 61-99), being 74% for QFT (95%CI: 47-95). Conclusions This is one of the first studies to estimate the prevalence of LTBI in children and the parameters of the main diagnostic tests using a latent class model. Our results suggest that children in contact with an index case have a high risk of infection. The accuracy and the predictive value of the two tests did not significantly differ. Combined use of the two tests showed scarce improvement in the diagnosis of LTBI

Pervasive surveillance-agent system based on wireless sensor networks: design and deployment

Nowadays, proliferation of embedded systems is enhancing the possibilities of gathering information by using wireless sensor networks (WSNs). Flexibility and ease of installation make these kinds of pervasive networks suitable for security and surveillance environments. Moreover, the risk for humans to be exposed to these functions is minimized when using these networks. In this paper, a virtual perimeter surveillance agent, which has been designed to detect any person crossing an invisible barrier around a marked perimeter and send an alarm notification to the security staff, is presented. This agent works in a state of 'low power consumption' until there is a crossing on the perimeter. In our approach, the 'intelligence' of the agent has been distributed by using mobile nodes in order to discern the cause of the event of presence. This feature contributes to saving both processing resources and power consumption since the required code that detects presence is the only system installed. The research work described in this paper illustrates our experience in the development of a surveillance system using WNSs for a practical application as well as its evaluation in real-world deployments. This mechanism plays an important role in providing confidence in ensuring safety to our environment

Reflexiones en torno a la sociedad, violencia y educación

El presente artículo reflexiona sobre la necesidad imperiosa de cuestionar aquellos aspectos propios de una sociedad patriarcal como espacio de relación de los y las adolescentes. Fruto del trabajo de las investigaciones cualitativas que venimos desarrollando, se detecta la persistencia de un sistema patriarcal que dificulta el desarrollo de relaciones igualitarias. Se hace pues, necesario, conocer esta realidad para así plantear propuestas educativas que favorezcan el crecimiento de los niños y niñas en modelos de relación igualitario