Detección electroquímica de peróxido de hidrógeno usando peroxidasa de pasto Guinea (Panicum maximum) inmovilizada sobre electrodos serigrafiados de puntos cuánticos

Electrochemical biosensors are analytical tools of fast and reliable response that have acquired interest in the last years due to the possibility of integrating biomolecules and electrodes made of nanometric materials. In this study, an electrochemical biosensor to detect hydrogen peroxide (H2O2) based on Guinea Grass peroxidase (GGP) immobilized on screen-printed quantum dots electrodes (SPQDE) was developed. GGP was partially purified from Guinea grass leaves having a specific activity of 602 U mg-1.Then, GGP was immobilized by physical adsorption on the surface on SPQDE and the electrochemical behavior was carried out through cyclic voltammetry and chronoamperometry techniques. GGP revealed a well-defined pair of redox signals at 17mV/-141mV corresponding to the redox process of the heme group (Fe2+/Fe3+) of peroxidases. The bioelectrocatalytic reduction of H2O2 has a redox potential of -645 mV vs Ag. This process was controlled by the diffusion of the species on the electrode surface using a scan rate range of 50-500 mV s. Chronoamperometry studies allow us the construction of calibration curves of reduction current vs H2O2 concentration for the determination of analytical parameters such as sensitivity, linear range and minimum detection level. The development of this amperometric biosensor becomes a preliminary step for the construction of a portable and rapid response device for the analysis of H2O2 in samples of environmental and biomedical interest.Os biossensores eletroquímicos são ferramentas analíticas de resposta rápida e confiável que adquiriram interesse especial nos últimos anos, graças à possibilidade de integrar biomoléculas com eletrodos feitos de materiais nanométricos. Neste trabalho, um biossensor eletroquímico foi desenvolvido para a detecção de peróxido de hidrogênio (H2O2) usando peroxidase do capim-da-Guiné (PPG) imobilizada em eletrodos serigráficos de pontos quânticos (ESPC) serigrafados. O PPG foi isolado e parcialmente purificado a partir de folhas de capim-da-Guiné com atividade específica de 602 U mg-1. Posteriormente, o PPG foi imobilizado na superfície do ESPC por adsorção física e estudo do comportamento eletroquímico foi realizado por voltametria cíclica e cronoamperometria. O PPG revelou um par bem definido de sinais redox em 17mV/-141mV correspondente ao processo redox do grupo heme (Fe2+/Fe3+) de peroxidases. A redução bioeletrocatalítica do H2O2 foi observada com um potencial redox de -645 mV vs. Ag. Esse processo foi controlado pela difusão das espécies na superfície do eletrodo em uma faixa de velocidade de varredura linear de 50-500 mV/s. A cronoamperometria permitiu a construção de curvas de calibração entre a corrente de redução e a concentração de H2O2 para a determinação de parâmetros analíticos como sensibilidade, faixa linear e nível mínimo de detecção. O desenvolvimento deste biossensor amperométrico torna-se uma etapa preliminar para a construção de um dispositivo portátil e de resposta rápida para a análise de H2O2 em amostras de interesse ambiental e biomédico.Los biosensores electroquímicos son herramientas analíticas de rápida y confiable respuesta que han adquirido especial interés en los últimos años gracias a la posibilidad de integrar biomoléculas con electrodos hechos a base de materiales nanométricos. En este trabajo se desarrolló un biosensor electroquímico para detección de peróxido de hidrógeno (H2O2) usando peroxidasa de pasto Guinea (PPG) inmovilizada sobre electrodos serigrafiados de puntos cuánticos (ESPC). La PPG fue aislada y parcialmente purificada a partir de hojas de pasto Guinea con una actividad específica de 602 Umg-1. Posteriormente, la PPG fue inmovilizada sobre la superficie del ESPC mediante adsorción física y el estudio del comportamiento electroquímico fue llevado a cabo mediante voltamperometría cíclica y cronoamperometría. La PPG reveló una pareja bien definida de señales redox a 17mV/-141mV correspondientes al proceso redox del grupo hemo (Fe2+/Fe3+) de las peroxidasas. La reducción bioelectrocatalítica del peróxido de hidrógeno se observó a un potencial redox de -645 mV vs Ag. Este proceso fue controlado por difusión de las especies en la superficie del electrodo en un rango de velocidad de barrido lineal de 50-500 mV/s. La cronoamperometría permitió la construcción de curvas de calibración entre la corriente de reducción y la concentración del H2O2 para la determinación de parámetros analíticos como sensibilidad, rango lineal y nivel mínimo de detección. El desarrollo de este biosensor amperométrico se convierte en un paso preliminar para la construcción de un dispositivo portátil y de respuesta rápida para el análisis de H2O2 en muestras de interés ambiental y biomédico

Aportes al conocimiento del sistema productivo de cultivo de la mora (Rubus glaucus Benth) en Colombia

Varios estudios que examinan el cultivo de la mora en Colombia muestran que esta actividad es realizada por pequeños y medianos agricultores. En muchas regiones constituye una de las principales fuentes de ingresos; generación de empleo rural; oferta de alimento y de agroindustria. En este trabajo se revisaron más de 180 documentos distribuidos entre artículos divulgativos, técnicos y científicos, publicados en boletines, manuales, cartillas, seminarios y cursos; además, resultados de trabajos de investigación, tesis de pregrado y artículos científicos publicados en revistas seriadas e indexadas. Este es resultado de la búsqueda la literatura de la agronomía del sistema productivo de la mora en la red, en la Biblioteca Agropecuaria de Colombia (BAC), en las bibliotecas de de la Universidad Nacional de Colombia y en las bibliotecas de los investigadores del CI La Selva de Corpoica. Para analizar la literatura sobre la agronomía y las prácticas de manejo agronómico de la mora (distribución espacial, trazado y siembra, propagación, tutorado, poda, entre otras). Del manejo agronómico se han escrito diversas publicaciones unas más profundas que otras, estas se caracterizan porque para la mayoría de las practicas agronómicas se carece de un sustento que las valide, para los diferentes ambiente y genotipos y muchas de ellas son el resultado de la observación, del sentido común y de adaptación de otro sistema productivo. Esta literatura surge en la década de 50’s, en la de los 70’ se dan las versiones más integrales del sistema productivo y durante la década de los 90’s, es el periodo dorado cuando se consolida y se presentan los trabajos mas completos, aun todavía faltando, la integralidad entre genotipo, ambiente y la interacción entre estos.Mora-Rubus ulmifoliu

Structure and non-structure of centrosomal proteins

Here we perform a large-scale study of the structural properties and the expression of proteins that constitute the human Centrosome. Centrosomal proteins tend to be larger than generic human proteins (control set), since their genes contain in average more exons (20.3 versus 14.6). They are rich in predicted disordered regions, which cover 57% of their length, compared to 39% in the general human proteome. They also contain several regions that are dually predicted to be disordered and coiled-coil at the same time: 55 proteins (15%) contain disordered and coiled-coil fragments that cover more than 20% of their length. Helices prevail over strands in regions homologous to known structures (47% predicted helical residues against 17% predicted as strands), and even more in the whole centrosomal proteome (52% against 7%), while for control human proteins 34.5% of the residues are predicted as helical and 12.8% are predicted as strands. This difference is mainly due to residues predicted as disordered and helical (30% in centrosomal and 9.4% in control proteins), which may correspond to alpha-helix forming molecular recognition features (α-MoRFs). We performed expression assays for 120 full-length centrosomal proteins and 72 domain constructs that we have predicted to be globular. These full-length proteins are often insoluble: Only 39 out of 120 expressed proteins (32%) and 19 out of 72 domains (26%) were soluble. We built or retrieved structural models for 277 out of 361 human proteins whose centrosomal localization has been experimentally verified. We could not find any suitable structural template with more than 20% sequence identity for 84 centrosomal proteins (23%), for which around 74% of the residues are predicted to be disordered or coiled-coils. The three-dimensional models that we built are available at http://ub.cbm.uam.es/centrosome/models/index.php

Regulatory T Cells in the Pathogenesis and Healing of Chronic Human Dermal Leishmaniasis Caused by Leishmania (Viannia) Species

The immune inflammatory response is a double edged sword. During infectious diseases, regulatory T cells can prevent eradication of the pathogen but can also limit inflammation and tissue damage. We investigated the role of regulatory T cells in chronic dermal leishmaniasis caused by species of the parasite Leishmania that are endemic in South and Central America. We found that although individuals with chronic lesions have increased regulatory T cells in their blood and at skin sites where immune responses to Leishmania were taking place compared to infected individuals who do not develop disease, their capacity to control the inflammatory response to Leishmania was inferior. However, healing of chronic lesions at the end of treatment was accompanied by an increase in the number and capacity of regulatory T cells to inhibit the function of effector T cells that mediate the inflammatory response. Different subsets of regulatory T cells, defined by the expression of molecular markers, were identified during chronic disease and healing, supporting the participation of distinct regulatory T cells in the development of disease and the control of inflammation during the healing response. Immunotherapeutic strategies may allow these regulatory T cell subsets to be mobilized or mitigated to achieve healing

American oil palm from Brazil: genetic diversity, population structure, and core collection.

The American oil palm [Elaeis oleifera (Knuth) Cortés] has pronounced importance in oil palm breeding programs. Here, a germplasm bank (GB) of E. oleifera plants collected in the Amazon rainforest in Brazil was submitted to single nucleotide polymorphism (SNP) marker identification, selection, and use, aiming to characterize genetic diversity and population structure and to design a core collection (CC). Five hundred and fifty-three plants from 206 subsamples, collected at 19 localities spread throughout six geographic regions, were submitted to genotyping-by-sequencing analysis. A set of 1,827 high-quality SNP markers was then selected and used to run the genetic diversity and population structure analysis. The genetic diversity found is of moderate degree, and probably only a small portion of the species diversity is represented in the collection. The possible reason for that is the collecting strategy used, which collected subsamples only around the most prominent watercourses in the region. The average degree of genetic differentiation among subsamples is very high, indicating the presence of high interpopulation differentiation. The collection showed a low level of endogamy. The low average gene flow found indicates that genetic isolation caused by drift is occurring, and there is a need to review the conservation strategy. A set of 245 SNPs distributed throughout all 16 chromosomes was used to design CC based on maximizing the strategy of diversity. The optimal adjustment of the validated parameters, maintained while taking fewest subsamples, led to the choice of a model containing 20% of the entire collection as the ideal to form the CC

Establishment phase, spatial pattern, age, and demography of Oenocarpus bataua var. bataua can be a legacy of past loggings in the Colombian Andes

Oenocarpus bataua var. bataua is a key species in the tropical rain forests of South America because it is one of the 10 most abundant tree species and one of most used by Amerindians. However, there is an acute lack of verifiable information about the duration of some of its ontogenic phases, the exact age of the palms, and the effect of gap formation on its spatial distribution. We employed 36 permanent plots (PP) of 0.1 ha randomly distributed in a forest of 700 ha in the Colombian Andes, in which we inventoried the stemmed palms at the establishment of the PP and after 13.4 years to study some ontogenic and demographic traits of this species. We dated underground and aboveground stems using the 14C bomb-effect and estimated the stem’s age by the rate of leaf-scar formation. We aimed at answering the following questions: (i) what are the main morphological characteristics of the underground stem and how long does it takes for its formation?; (ii) what is the pattern of its spatial distribution at the landscape level, and what factors help to explain it?; (iii) is the population structure and demography associated with the previous history of the forest?; (iv) is the first flowering a function of the vigour of the palms?. We found that the underground stem of adult palms is usually obconical and reaches 73 ± 13 cm in length (±standard deviation). The duration of the establishment phase in eleven palms was almost constant: 37.5 ± 0.7 years. The palms with smaller and larger diameters tend to flourish when the stems are 18 and 7 years old (44–55 years old from seedlings), respectively. We found that this species has a clumped spatial pattern. Several palms dated gave ages between 91 and 92 years, while others about 53 years. The bell shaped frequency distribution of the palm’s length and age suggest a lack of younger palms in this area. We interpret that both, the clumped spatial pattern and their age distribution, are a legacy from past selective loggings that induced even-aged cohorts of palms at the landscape level. This species is not in equilibrium because the population tends to be reduced through time given that its doubling time is 37.4 years and its half-life 29.3 year

Unambiguous and low-cost determination of growth rates and ages of tropical trees and palms

The determination of the age of tropical trees and palms is of significant importance for ecological studies and designing sustainable forest management plans. Radiocarbon is a powerful tool that can potentially help the determination of ages and growth rates of these organisms. However, the application of radiocarbon analyses has one important problem for trees without annual rings and palms: the calibration of radiocarbon measurements with common programs such as Calibomb or OxCal gives erroneous determinations for wood formed before 1964 AD. We illustrate here this problem using samples from a tropical tree (Otoba gracilipes) and a tropical palm (Oenocarpus bataua). We show how the use of two adjacent samples can help to unambiguously determine the real age of the samples and their mean growth rates. For comparison, we used long-term growth measurements for both species and conclude that radiocarbon analyses provide accurate determination of growth rates for trees and palms. Furthermore, the application of radiocarbon analyses in palms allows the determination of the rosette-stage in palms, a stage rarely quantified in forest inventories

A General-Purpose Element-Based Approach to Compute Dispersion Relations in Periodic Materials with Existing Finite Element Codes

The numerical determination of dispersion relations in periodic materials via the finite element method is a difficult task in most standard codes. Here, we propose a novel technique which allows the computation of these band structures from local elemental subroutines in contrast with existing methods which impose Bloch boundary conditions on the global arrays. The proposed local approach is thus readily applicable to several physical contexts and space dimensionalities. Here we present the details of this element-based algorithm and provide verification results for three different kinematic assumptions applied to phononic crystals in a classical and a micropolar elastic medium. The paper also includes in the form of supplementary material, a fully-coded user subroutine and a test-problem to be used in a commercial finite element code. © 2019 IMACS