Radiolysis of Nucleosides: Study of Sedimentary Microenvironment Models for the Protection of Bio-Organic Molecules on Early Earth

Nucleic acid bases and their derivatives are important compounds in biological systems. Many efforts have been made to demonstrate the possible prebiotic origin of these molecules, but the abiotic synthesis of these compounds has proved to be very difficult in that conditions. So, if their synthesis actually took place, a study of their stability in prebiotic conditions is quite relevant in chemical evolution studies. In this work, it has been examined and compared the influence of Sodium Montmorillonite on the chemical transformations undergone by two nucleosides (guanosine –purinic– and uridine, –pyrimidinic–) when subjected to conditions simulating the primitive Earth during the period of chemical evolution. The experiments prove the concentration capacity and protective role against external sources of ionizing radiation (specifically γ-ray) that clays can provide to these specific compounds adsorbed on them. By using X-ray diffraction, UV-vis spectrophotometry and HPLC for the analysis, it was found that purinic nucleosides (more than pyrimidinic) are quickly adsorbed on clay at low pH values, and the temperature of mineral desiccation applied after adsorption promotes their decomposition into their corresponding nitrogenous bases. In both, purinic and pyrimidinic, desorption occurs in neutral or slightly basic aqueous solutions, and both are protected by clay. Pyrimidinic nucleosides show more resistance to heat, but less resistance towards ionizing radiation, even when adsorbed in clay

Ionizing Radiation, an Instrument in Chemical Evolution Studies: Scope and Perspectives

The study of synthesis and stability of molecules in different environments it’s been part of chemistry evolution and origin of life studies for more than 70 years. Various kinds of ionizing radiation have been analyzed as possible sources of energy for the transformations undergone by the first organic molecules. Now experimental and computational simulation approaches continue with different groups of organic molecules, in search for more information that help us to understand and reconstruct somehow the mechanisms that toke place on early Earth and space. In that line, this paper presents first approach of keto acids stability to ionizing radiation, an interesting group of molecules involved in the Krebs cycle and glycolysis. Preliminary results obtained by HPLC/UV analysis of irradiating aqueous solutions of 5 keto acids ranging from 3 to 6 carbons with a 60Co gamma ray source, using doses up to 53 kGy, show different stabilities and a general tendency of shifting the keto-enol equilibrium to the enol tautomer before decomposition

Development of a dispersive liquid-liquid microextraction coupled with magnetic dispersive microsolid phase extraction for determination of triazines in wastewater samples

Producción CientíficaThe combination of two microextraction techniques (dispersive liquid-liquid microextraction [DLLME] and magnetic dispersivemicrosolid phase extraction [MDMSPE]) was developed and reported for atrazine and simazine preconcentration from wastewatersamples. The proposal methodology involved the use of magnetite supports functionalized with different alkyl or phenyl groups. Themagnetic adsorbents were synthesized by the solvothermal methodassisted by microwave, characterized, and used in the samplepreconcentration of atrazine and simazine. The method validation included parameters such as the wastewater matrix effect, repeat-ability, and recovery. The analyte separation and quantification were performed by high-performance liquid chromatography withultraviolet detection (HPLC-DAD). Parameters, such as the polarity and mass of magnetic solids and pH, were evaluated to providebetter extraction performance. The highest recoveries (> 95%) were obtained with 50 mg of the phenyl group support (CS2) at pH 5,using 5 mL of the sample and carbon tetrachloride and methanol, as extraction and dispersive solvents, respectively. The lowest limitsof detection (LOD) achieved were 13.16 and 13.86 ng L−1, and the limits of quantification (LOQ) were 43.89 and 46.19 ng L−1forsimazine and atrazine, respectively, with repeatability (expressed as %RSD) below 5% in all cases. The developed method is simple,easy, and low cost for the analysis of two herbicides potentially dangerous for environmental and human health

Facile synthesis of low band gap ZnO Microstructures

Abstract In this work a simple chemical route was employed to synthesize ZnO microparticles by precipitation from aqueous solution of ZnCl2 as precursor, NaOH as oxidizing and sodium dodecyl sulfate (SDS) as surfactant. Samples of ZnO microparticles were analyzed by scanning electron microscopy (SEM), FTIR spectroscopy, Raman spectroscopy, X-Ray diffraction, UV/Vis-NIR diffusereflectance,highresolutiontransmissionelectronmicroscopy(HR-TEM),andN2 adsorption-desorption.Itwasobserved from SEM analysis that ZnO microparticles with morphologies resembling six-blade impeller with diameters in the range of 500 nm to 1 m, and sheet-like (approximately 200 nm×300 nm) were obtained through this technique. X-Ray diffraction and Raman analyses confirmed the obtaining of hexagonal wurtzite ZnO crystal structure. The calculated band gap energy was 3.19 eV, which is slightly lower than the average value reported in the literature. Specific BET area of ZnO microparticles was 26.5 m2/g. Keywords: ZnO, microstructures, band gap energy, SEM, morphology. Resumen En este trabajo se empleó un a ruta química sencilla para sintetizar micropartículas de ZnO mediante precipitación en solución acuosa de ZnCl2 como precursor, NaOH como oxidante y dodecil sulfato de sodio (SDS) como tensoactivo. Las muestras de ZnO fueron analizadas mediante microscopía de barrido electrónico (SEM), espectroscopía de FTIR, espectroscopía Raman, difracción de rayos-X, reflectancia difusa de UV/Vis-NIR, microscopía de transmisión de electrones de alta resolución (HRTEM), y mediante adsorción-desorción de N2. Se observó mediante análisis de SEM que mediante esta técnica se obtienen micropartículas de ZnO con morfologías similares a impulsores de seis-aspas con diámetros entre 500 nm y 1 m, morfologías tipo-hojas(deaproximadamente200nm×300nm).Losanálisisdedifracciónderayos-XydeRamanconfirmaronlaobtención de ZnO con estructura cristalina wurtzita hexagonal. La energía de band gap calculada fue de 3.19 eV, la cual es ligeramente menor que el valor promedio reportado en la literatura. El área superficial BET de las nanopartículas de ZnO fue de 26.5 m2/g Palabras clave: ZnO, microestructuras, energía de band gap, SEM, morfología

Aguas del Iténez o Guaporé

Bolivia y Brasil comparten una de las cuencas más atractivas y preservadas de la te-giuri amazônica: la cuenca del rio llénez o Guaporé, que escurre tanto sobre el lecho rocoso del Escudo Precámbrico Brasilefto como sobre las Hanuras del Beni. Estas influencias hacen que la cuenca del iténez tenga una elevada heterogeneidad de habitats, una fauna acuálica peculiar y un alto valor de conservation. Este patrimo­nio binacional posée un potencial importante para la conservación de la diversidad regional y cl dcsar rollo sostcniblc participativo de las comunidades locales. El libro contiene un resumen del conotimìento de la cuenca y sus recursos, generado en los últimos 10 anos por un equipo de investigadores bolivianos, brasilefios y de otras nacionalidades. Se presenta una descripeión del medio fisico, así como resultados relevantes sobre la biodiversidad acuática, con énfasis en algas, peces, reptiles y mamíferos. El aporte más notable del libro, adernas de la descripeión ecológica del ecosistema, son las lecciones aprendidas que surgieron de experiências locales sobre la élaboration participativa de herramientas para la gestion de los recursos hidrobiológicos.A Bolívia e o Brasil compartilham uma das bacias hidrográficas mais atrativas e preservadas da região amazônica: a bacia do Rio Iténez ou Guaporé. A combinação das influências do escudo pré-cambriano brasileiro e da planícies do Beni é uma das razões pela qual existem na região elevada heterogeneidade de habitats, fauna aquática peculiar e alto grau valor dc conservação. Eslc patrimônio binacional possui potencial significativo para a conservação da diversidade regional e desenvolvimento sustentável participativo das comunidades locais. O livro contém um resumo do conhecimento da bacia e seus recursos, gerado nos últimos dez anos por uma equipe de pesquisadores bolivianos, brasileiros e de outras nacionalidades. Apresentamos uma descrição do meio físico, bem como resultados relevantes da biodiversidade aquática, com ênfase em algas, peixes, répteis e mamíferos. A contribuição mais notável do livro, além da descrição ecológica do ecossistema, é a descrição das lições aprendidas que surgiram a partir de experiências locais sobre elaboração participativa de ferramentas para a gestão dos recursos aquáticos presentes nesta bacia

La investigación universitaria y sus contribuciones en Mesoamérica

La Universidad Autónoma de Chiapas a través de su Proyecto Académico 2014-2018, reafirma su compromiso con el desarrollo de nuestra región, al establecer líneas de desarrollo de nuestra región, al establecer líneas de desarrollo institucional, donde la vinculación de la investigación ocupa un lugar preponderante; en este sentido, a partir de 2015, junto con la comunidad académica internacional, se unió a la Agenda 2030 para el Desarrollo sostenible de la ONU y priorizó los 17 Objetivos de Desarrollo Sostenible (ODS) y sus 169 metas, con la finalidad de dar soluciona los grandes desafíos sociales, económicos y medioambientales que enfrenta la sociedad. Este libro es la recopilación de trabajos realizados por académicos de diversas Instituciones de Educación Superior y Centros de Investigación, de manera multidisciplinaria, interinstitucional e internacional, los cuales han permitido compartir intereses en diversas líneas de generación y aplicación del conocimiento

La investigación universitaria y sus contribuciones en Mesoamérica

La Universidad Autónoma de Chiapas a través de su Proyecto Académico 2014-2018, reafirma su compromiso con el desarrollo de nuestra región, al establecer líneas de desarrollo de nuestra región, al establecer líneas de desarrollo institucional, donde la vinculación de la investigación ocupa un lugar preponderante; en este sentido, a partir de 2015, junto con la comunidad académica internacional, se unió a la Agenda 2030 para el Desarrollo sostenible de la ONU y priorizó los 17 Objetivos de Desarrollo Sostenible (ODS) y sus 169 metas, con la finalidad de dar soluciona los grandes desafíos sociales, económicos y medioambientales que enfrenta la sociedad. Este libro es la recopilación de trabajos realizados por académicos de diversas Instituciones de Educación Superior y Centros de Investigación, de manera multidisciplinaria, interinstitucional e internacional, los cuales han permitido compartir intereses en diversas líneas de generación y aplicación del conocimiento