Adsorption and catalytic activity of glucose oxidase accumulated on OTCE upon the application of external potential

This article describes the adsorption of glucose oxidase (GOx) onto optically transparent carbon electrodes (OTCE) under the effect of applied potential and the analysis of the enzymatic activity of the resulting GOx/OTCE substrates. In order to avoid electrochemical interferences with the enzyme redox center, control electrochemical experiments were performed using flavin adenine dinucleotide (FAD) and GOx/OTCE substrates. Then, the enzyme adsorption experiments were carried out as a function of the potential applied (ranged from the open circuit potential to +950. mV), the pH solution, the concentration of enzyme, and the ionic strength on the environment. The experimental results demonstrated that an increase in the adsorbed amount of GOx on the OTCE can be achieved when the potential was applied. Although the increase in the adsorbed amount was examined as a function of the potential, a maximum enzymatic activity was observed in the GOx/OTCE substrate achieved at +800. mV. These experiments suggest that although an increase in the amount of enzyme adsorbed can be obtained by the application of an external potential to the electrode, the magnitude of such potential can produce detrimental effects in the conformation of the adsorbed protein and should be carefully considered. As such, the article describes a simple and rational approach to increase the amount of enzyme adsorbed on a surface and can be applied to improve the sensitivity of a variety of biosensors.Fil: Benavidez, Tomás Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. University of Texas; Estados UnidosFil: Torrente, Daniel. University of Texas; Estados UnidosFil: Marucho, Marcelo. University of Texas; Estados UnidosFil: Garcia, Carlos D.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. University of Texas; Estados Unido

Dielectric Spectroscopy can Predict the Effect of External AC Fields on the Dynamic Adsorption of Lysozyme

This report describes the application of dielectric spectroscopy as a simple and fast way to guide protein adsorption experiments. Specifically, the polarization behavior of a layer of adsorbed lysozyme was investigated using a triangular-wave signal with frequencies varying from 0.5 to 2 Hz. The basic experiment, which can be performed in less than 5 min and with a single sample, not only allowed confirming the susceptibility of the selected protein towards the electric signal but also identified that this protein would respond more efficiently to signals with lower frequencies. To verify the validity of these observations, the adsorption behavior of lysozyme onto optically transparent carbon electrodes was also investigated under the influence of an applied alternating potential. In these experiments, the applied signal was defined by a sinusoidal wave with an amplitude of 100 mV and superimposed to +800 mV (applied as a working potential) and varying the frequency in the 0.1–10000 Hz range. The experimental data showed that the greatest adsorbed amounts of lysozyme were obtained at the lowest tested frequencies (0.1–1.0 Hz), results that are in line with the corresponding dielectric features of the protein.Fil: Benavidez, Tomás Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Guerra, José D. S.. Universidade Federal de Uberlandia; BrasilFil: Garcia, Carlos D.. CLEMSON UNIVERSITY (CLEMSON UNIVERSITY)

A review of the (Revised) Universal Soil Loss Equation ((R)USLE): with a view to increasing its global applicability and improving soil loss estimates

Soil erosion is a major problem around the world because of its effects on soil productivity, nutrient loss, siltation in water bodies, and degradation of water quality. By understanding the driving forces behind soil erosion, we can more easily identify erosion-prone areas within a landscape to address the problem strategically. Soil erosion models have been used to assist in this task. One of the most commonly used soil erosion models is the Universal Soil Loss Equation (USLE) and its family of models: the Revised Universal Soil Loss Equation (RUSLE), the Revised Universal Soil Loss Equation version 2 (RUSLE2), and the Modified Universal Soil Loss Equation (MUSLE). This paper reviews the different sub-factors of USLE and RUSLE, and analyses how different studies around the world have adapted the equations to local conditions. We compiled these studies and equations to serve as a reference for other researchers working with (R)USLE and related approaches. Within each sub-factor section, the strengths and limitations of the different equations are discussed, and guidance is given as to which equations may be most appropriate for particular climate types, spatial resolution, and temporal scale. We investigate some of the limitations of existing (R)USLE formulations, such as uncertainty issues given the simple empirical nature of the model and many of its sub-components; uncertainty issues around data availability; and its inability to account for soil loss from gully erosion, mass wasting events, or predicting potential sediment yields to streams. Recommendations on how to overcome some of the uncertainties associated with the model are given. Several key future directions to refine it are outlined: e.g. incorporating soil loss from other types of soil erosion, estimating soil loss at sub-annual temporal scales, and compiling consistent units for the future literature to reduce confusion and errors caused by mismatching units. The potential of combining (R)USLE with the Compound Topographic Index (CTI) and sediment delivery ratio (SDR) to account for gully erosion and sediment yield to streams respectively is discussed. Overall, the aim of this paper is to review the (R)USLE and its sub-factors, and to elucidate the caveats, limitations, and recommendations for future applications of these soil erosion models. We hope these recommendations will help researchers more robustly apply (R)USLE in a range of geoclimatic regions with varying data availability, and modelling different land cover scenarios at finer spatial and temporal scales (e.g. at the field scale with different cropping options).</p

A mid-term astrometric and photometric study of Trans-Neptunian Object (90482) Orcus

From CCD observations of a fixed and large star field that contained the binary TNO Orcus, we have been able to derive high-precision relative astrometry and photometry of the Orcus system with respect to background stars. The RA residuals of an orbital fit to the astrometric data revealed a periodicity of 9.7+-0.3 days, which is what one would expect to be induced by the known Orcus companion. The residuals are also correlated with the theoretical positions of the satellite with regard to the primary. We therefore have revealed the presence of Orcus' satellite in our astrometric measurements. The photocenter motion is much larger than the motion of Orcus around the barycenter, and we show here that detecting some binaries through a carefully devised astrometric technique might be feasible with telescopes of moderate size. We also analyzed the system's mid-term photometry to determine whether the rotation could be tidally locked to the satellite's orbital period. We found that a photometric variability of 9.7+-0.3 days is clear in our data, and is nearly coincident with the orbital period of the satellite. We believe this variability might be induced by the satellite's rotation. There is also a slight hint for an additional small variability in the 10 hr range that was already reported in the literature. This short-term variability would indicate that the primary is not tidally locked and therefore the system would not have reached a double synchronous state. Implications for the basic physical properties of the primary and its satellite are discussed. From angular momentum considerations we suspect that the Orcus satellite might have formed from a rotational fission. This requires that the mass of the satellite would be around 0.09 times that of the primary, close to the value that one derives by using an albedo of 0.12 for the satellite and assuming equal densities for both objects.Comment: in Press at A&

Fluorescent patterning of paper through laser engraving

While thermal treatment of paper can lead to the formation of aromatic structures via hydrothermal treatment (low temperature) or pyrolysis (high temperature), neither of these approaches allow patterning the substrates. Somewhere in between these two extremes, a handful of research groups have used CO2 lasers to pattern paper and induce carbonization. However, none of the previously reported papers have focused on the possibility to form fluorescent derivatives via laser-thermal engraving. Exploring this possibility, this article describes the possibility of using a CO2 laser engraver to selectively treat paper, resulting in the formation of fluorescent compounds, similar to those present on the surface of carbon dots. To determine the most relevant variables controlling this process, 3 MM chromatography paper was treated using a standard 30 W CO2 laser engraver. Under selected experimental conditions, a blue fluorescent pattern was observed when the substrate was irradiated with UV light (365 nm). The effect of various experimental conditions (engraving speed, engraving power, and number of engraving steps) was investigated to maximize the fluorescence intensity. Through a comprehensive characterization effort, it was determined that 5-(hydroxymethyl)furfural and a handful of related compounds were formed (varying in amount) under all selected experimental conditions. To illustrate the potential advantages of this strategy, that could complement those applications traditionally developed from carbon dots (sensors, currency marking, etc.), a redox-based optical sensor for sodium hypochlorite was developed.Fil: Clark, Kaylee M.. Clemson University; Estados UnidosFil: Skrajewski, Lauren. Clemson University; Estados UnidosFil: Benavidez, Tomás Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Clemson University; Estados UnidosFil: Mendes, Letícia F.. Universidade de Sao Paulo; BrasilFil: Bastos, Erick L.. Universidade de Sao Paulo; BrasilFil: Dörr, Felipe A.. Universidade de Sao Paulo; BrasilFil: Sachdeva, Rakesh. Clemson University; Estados UnidosFil: Ogale, Amod A.. Clemson University; Estados UnidosFil: Paixão, Thiago R. L. C.. Universidade de Sao Paulo; BrasilFil: Garcia, Carlos D.. Clemson University; Estados Unido

Rotational fission of Trans-Neptunian Objects. The case of Haumea

We present several lines of evidence based on different kinds of observations to conclude that rotational fission has likely occurred for a fraction of the known Trans-Neptunian Objects (TNOs). It is also likely that a number of binary systems have formed from that process in the trans-neptunian belt. We show that Haumea is a potential example of an object that has suffered a rotational fission. Its current fast spin would be a slight evolution of a primordial fast spin, rather than the result of a catastrophic collision, because the percentage of objects rotating faster than 4 hours would not be small in a maxwellian distribution of spin rates that fits the current TNO rotation database. On the other hand, the specific total angular momentum of Haumea and its satellites falls close to that of the high size ratio asteroid binaries, which are thought to be the result of rotational fissions or mass shedding. We also present N-body simulations of rotational fissions applied to the case of Haumea, which show that this process is feasible, might have generated satellites, and might have even created a "family" of bodies orbitally associated to Haumea. The orbitally associated bodies may come from the direct ejection of fragments according to our simulations, or through the evolution of a proto-satellite formed during the fission event. Also, the disruption of an escaped fragment after the fission might create the orbitally related bodies. If any of those mechanisms are correct, other rotational fission families may be detectable in the trans-neptunian belt in the future, and perhaps even TNO pairs might be found (pairs of bodies sharing very similar orbital elements, but not bound together)

Adaptation of Microelectrode Array Technology for the Study of Anesthesia-Induced Neurotoxicity in the Intact Piglet Brain

Every year, millions of children undergo anesthesia for a multitude of procedures. However, studies in both animals and humans have called into question the safety of anesthesia in children, implicating anesthetics as potentially toxic to the brain in development. To date, no studies have successfully elucidated the mechanism(s) by which anesthesia may be neurotoxic. Animal studies allow investigation of such mechanisms, and neonatal piglets represent an excellent model to study these effects due to their striking developmental similarities to the human brain. This protocol adapts the use of enzyme-based microelectrode array (MEA) technology as a novel way to study the mechanism(s) of anesthesia-induced neurotoxicity (AIN). MEAs enable real-time monitoring of in vivo neurotransmitter activity and offer exceptional temporal and spatial resolution. It is hypothesized that anesthetic neurotoxicity is caused in part by glutamate dysregulation and MEAs offer a method to measure glutamate. The novel implementation of MEA technology in a piglet model presents a unique opportunity for the study of AIN

Consumo lácteo y su impacto en la salud ósea de población adulta en Colombia. Recomendaciones de la Asociación Colombiana de Osteoporosis y Metabolismo Mineral, basadas en la evidencia

El calcio es el mineral más abundante del cuerpo y está contenido, en su mayoría, en el esqueleto. La ingesta de este elemento depende de la edad y de la condición del individuo. En efecto, existe una alta deficiencia en el consumo de calcio en la dieta a nivel mundial y nacional, según los estudios recientes que motivaron a la Asociación Colombiana de Osteoporosis y Metabolismo Mineral (ACOMM) para la elaboración de este manuscrito. En el desarrollo de este texto, se contactaron especialistas de diferentes disciplinas, con interés académico en salud ósea y nutrición. Mediante la consulta de literatura científica, de bases de datos como Embase, Pubmed, Scielo y Google Académico, y con la asesoría de un epidemiólogo, se profundizó en las propiedades de los lácteos, las características de la leche y sus derivados, sus beneficios para la salud ósea (densidad ósea y prevención de fracturas) y el riesgo cardiovascular. Además, se registraron las recomendaciones del consumo lácteo para la población y se desmitificaron algunos conceptos que no tenían bases en la evidencia científica, los cuales han causado a una disminución en el consumo de calcio de la dieta, con un impacto negativo en la salud ósea

Evidence for multi-fragmentation and mass shedding of boulders on rubble-pile binary asteroid system (65803) Didymos.

Asteroids smaller than 10 km are thought to be rubble piles formed from the reaccumulation of fragments produced in the catastrophic disruption of parent bodies. Ground-based observations reveal that some of these asteroids are today binary systems, in which a smaller secondary orbits a larger primary asteroid. However, how these asteroids became binary systems remains unclear. Here, we report the analysis of boulders on the surface of the stony asteroid (65803) Didymos and its moonlet, Dimorphos, from data collected by the NASA DART mission. The size-frequency distribution of boulders larger than 5 m on Dimorphos and larger than 22.8 m on Didymos confirms that both asteroids are piles of fragments produced in the catastrophic disruption of their progenitors. Dimorphos boulders smaller than 5 m have size best-fit by a Weibull distribution, which we attribute to a multi-phase fragmentation process either occurring during coalescence or during surface evolution. The density per km2 of Dimorphos boulders ≥1 m is 2.3x with respect to the one obtained for (101955) Bennu, while it is 3.0x with respect to (162173) Ryugu. Such values increase once Dimorphos boulders ≥5 m are compared with Bennu (3.5x), Ryugu (3.9x) and (25143) Itokawa (5.1x). This is of interest in the context of asteroid studies because it means that contrarily to the single bodies visited so far, binary systems might be affected by subsequential fragmentation processes that largely increase their block density per km2. Direct comparison between the surface distribution and shapes of the boulders on Didymos and Dimorphos suggest that the latter inherited its material from the former. This finding supports the hypothesis that some asteroid binary systems form through the spin up and mass shedding of a fraction of the primary asteroid