Radiolysis of Serine in High Radiation Field

The formation of amino acids under simulated condition suggests that this type of compounds were readily formed on the primitive Earth. Nevertheless, there is no conclusive explanation to the origin of their specific chirality in biological systems. Differences in their stability in the primitive conditions may give some clues about this unsolved problem. Protection mechanisms have been considered, such as the adsorption of the organic compounds onto mineral surfaces. By using HPLC/ELSD to analyze aqueous suspensions of serine adsorbed on clay (sodium montmorillonite) and a meteorite (Allende) irradiated in different doses with a cobalt-60 gamma source, the aim of this work was to study the possible protector role of these mineral surfaces when an amino acid, serine, is adsorbed onto them and the system is exposed to a high radiation source. The results showed that adsorption is better at acidic pH and desorption from the mineral at basic pH. The irradiation of the free amino acid destroyed it almost completely at a dose of 91 kGy, but the presence of the mineral abruptly decreases the decomposition, acting as a protective agent. At the same time, the results in aqueous solution show no statistically significant differences in adsorption or radiolysis of D and L serine

Radiation Induced Oxidation Reactions of Ferrous Ions: An Agent-based Model

Chemical Fricke dosimeter in the laboratory can be submitted to gamma radiation at low temperatures to study the evolution of oxidation reactions induced by radiation, a key process to understand the formation of complex molecules. Products generated by the interaction of the different elements under radiation can be determined through a mathematical model that considers chemical reactions as coupled nonlinear ordinary differential equations involving the mass balance of all the species in the reaction. In this paper is implemented an alternative way of solving this system of equations, species’ concentrations are calculated through an agent-based model implemented in Python. The model is a modified version of the prey-predator model where each chemical specie involved is considered as an agent that can interact with other specie with known reaction rates leading to production (source terms) and to destruction (sink terms). Here, the radiation is a factor that affects product formation while the bath temperature modifies the reaction speed. This model can reproduce experimental concentrations of products and the consumption of ferrous ions from a laboratory reaction of irradiation of iron salt solutions at 3 different temperatures (dry ice, liquid nitrogen, and room temperature)

The Current Status of the Distribution Range of the Western Pine Beetle, Dendroctonus brevicomis (Curculionidae: Scolytinae) in Northern Mexico

Abstract The distribution range of the western pine beetle Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae) is supported only by scattered records in the northern parts of Mexico, suggesting that its populations may be marginal and rare in this region. In this study, we review the geographical distribution of D. brevicomis in northern Mexico and perform a geometric morphometric analysis of seminal rod shape to evaluate its reliability for identifying this species with respect to other members of the Dendroctonus frontalis Zimmermann (Coleoptera: Curculionidae) complex. Our results provide 30 new records, with 26 distributed in the Sierra Madre Occidental and 4 in the Sierra Madre Oriental. These records extend the known distribution range of D. brevicomis to Durango and Tamaulipas states in northern Mexico. Furthermore, we find high geographic variation in size and shape of the seminal rod, with conspicous differences among individuals from different geographical regions, namely west and east of the Great Basin and between mountain systems in Mexico. Key words: seminal rod shape, geometric morphometry, Dendroctonus frontalis comple

A tetraiodo cuprate NHC-MIC biscarbene proligand: coordination chemistry and preliminary catalysis

La preparación de una sal híbrida conteniendo cationes imidazolio/triazolio [NHC-MIC]²+ fue llevada a cabo en tres pasos sintéticos utilizando la cicloadición de azida-alquino catalizada por cobre (CuAAC) y la subsecuente N-metilación del 1,2,-3 triazol. Deprotonación selectiva de la sal mixta con NaH en presencia de un precursor metálico (M= Pd, Rh) permite la síntesis de NHC-metálicos conteniendo fragmentos catiónicos de tipo triazolio [NHC∙(M)-MIC]+. La subsecuente deprotonación del triazolio con KOᵗBu en presencia de Mpermite entonces la síntesis de complejos inusuales tipo quelato conteniendo carbenos clásicos tipo NHC y carbenos mesoiónicos MIC con estructura general [NHC∙(M)∙MIC]+MX₂-. Todos los compuestos han sido caracterizados mediante RMN de ¹H y ¹³C, FT-IR y cristalografía de rayos-X de monocristal. Estudios catalíticos preliminares de los nuevos complejos en procesos de formación de α-cetoamidas serán discutidos.A novel linked imidazolium/triazolium salt [NHC-MIC]²+ was preparedin three synthetic stepsusing copper catalyzed alkyne azide cycloaddition (CuAAC) and N-methylation protocols. Metallation of the imidazolium moiety using KHMDS in presence of a metallic precursor (M = Pd, Rh) yields NHC-anchored/pendent triazolium species [NHC∙(M)-MIC]+ in good yields. The subsequent deprotonation of the triazolium fragment with KOᵗBu in presence of one equivalent of M delivers the rare chelating mixed classical NHC/mesionic biscarbene complexes with the general formula [NHC∙(M)∙MIC]+MX₂-. All the complexes were fully characterized by ¹H and ¹³C NMR, FT-IR and single crystal X-ray diffraction. Preliminary catalytic performances of the new complexes in the oxidativepreparation of α-ketoamides will be discussed

Gamma Irradiation of Aqueos Solution of L-Aspartic Acid, L-Aspartic Acid in Solid State, and L-Aspartic Acid Adsorbed into Na-Montmorillonite: Its Relevance in Chemistry Prebiotic

Aspartic acid is an amino acid present in the modern proteins, however, is considered a primitive amino acid hence its importance in prebiotic chemistry experiments studies. In some works of prebiotic chemistry have been studied the synthesis and the stability of organic matter under high energy sources, and the role of clays has been highlighted due to clays that can affect the reaction mechanisms in the radiolytic processes. The present work is focused on the study of the role of Namontmorillonite in the gamma radiolysis processes of L-aspartic acid. Gamma radiolysis processes were carried out in three different systems a) L-aspartic acid in aqueous solution; b) L-aspartic acid in solid-state; and c) L-aspartic acid adsorbed into Na-montmorillonite. L-aspartic acid was analyzed by high-performance liquid chromatography−electrospray ionization−mass spectrometry (HPLCESI-MS). The results showed that the decomposition of L-aspartic acid considerably decreased in the presence of clay thus highlighting the protector role of clays and favors the stability of organic matter even under the possible high energy conditions of primitive environments. The principal product ofgamma radiolysis of L-aspartic acid was succinic acid produced by deamination reaction. On the other hand, when aspartic acid was irradiated in solid-state the main product was the L-aspartic acid dimer. Both radiolysis products are important for chemical evolution processes for L-aspartic acid in primitive environments

Síntesis e índices de reactividad de triazoles derivados de lactosa y las xantinas teofilina y teobromina

Mediante un sistema de reacción de cicloadición (3+2) regioselectiva, ha sido posible unir mediante una estructura principal de triazol a los grupos tipo carbohidrato –lactosa– y a los grupos derivados de la familia xantina – teobromina y teofilina– para obtener la síntesis del producto correspondiente. Se espera que este tipo de moléculas presenten actividad como inhibidores de la corrosión. Para su estudio y caracterización hemos usado los índices de reactividad globales basados en la Teoría de Funcionales de la Densidad (TFD) que han llegado a ser una poderosa herramienta para el estudio de la reactividad de compuestos orgánicos. Se muestran los siguientes parámetros como EHOMO, ELUMO, GAP, la dureza y el momento dipolar como indicadores del comportamiento inhibidor de la corrosión de las moléculas sintetizadas.Through a regioselective cycloaddition (3+2) reaction system, it has been possible to link the carbohydrate-lactose- like groups and the groups derived from the xanthine-theobromine and theophylline-family through a triazole structure corresponding product. It is expected that this type of molecules present activity as corrosion inhibitors. For its study and characterization, we have used the global reactivity indices based on the Theory of Density Functionalists (TFD) that have become a powerful tool for the study of the reactivity of organic compounds. The following parameters are shown as EHOMO, ELUMO, GAP, hardness and dipole moment as indicators of the corrosion inhibitory behavior of synthesized molecules

Quantitative Estimation of Black Carbon in the Glacier Ampay-Apurimac

The presence of light-absorbing particles, including black carbon in glaciers leads to a reduction in albedo (light reflection), leading to further melting of snow ice, increased amount of shortwave solar radiation and leads to the glacier. The objective has been to determine the variation in the temporal space of black carbon, the amount of light-absorbing particles and the decrease of albedo on the surface of the Ampay glacier. 10 snow samples were selected at various locations on the glacier during 2017. The light absorption heating method has been applied to measure light-absorbing particles, a technique that measures the temperature increase of the particle charge in a filter applying visible light that estimates the amount of light energy. The results show in terms of effective black carbon, the highest of 65,224 nanograms of black carbon per gram of water in the month of October and the minimum value of 20,941 nanograms of black carbon per gram of water in the month of February, typically associated with the rain. The energy absorbed by the light-absorbing particles in the Ampay glacier, the highest corresponds to the month of November with 8,952.92 J s/m2 and lowest in February with 2,747.26 J s/m2. In April, the amount of snow melted due to light-absorbing particles has been approximately 13.57 kg/m2. Melting has increased considerably in other months with the largest melting, with a value of 26.65 kg/m2, almost 7.0 kW/m2 of snow turned into water in the month of November. It is concluded that the technique of the Light absorption heating method is adequate because it is optimal for the achievement of the research objectives, it is economical, effective and has allowed quantifying light-absorbing particles in snow

Síntesis de etinil estradiol y su aplicación en una reacción de ciclo adición catalizada por Cu(I)

El etinilestradiol es un esteroide común en medicamentos de terapia y regulación hormonal y contiene en su estructura un grupo alquino en el carbono 17 que permite llevar a cabo una reacción de ciclo adición [3+2] para la obtención de 1, 2, 3 triazoles. En este trabajo se describe una metodología alternativa para la obtención del etinilestradiol a partir de estrona mediante una reacción de Grignard empleando como nucleófilo al bromuro de etilinilmagnesio, este derivado se utilizó como sintón para la formación de un triazol hibrido compuesto de un esteroide y un azida derivada de carbohidrato (3-azida-1,2:5,6-diisopropiliden--D-glucofuranosa) bajo condiciones de térmicas clásicas. Los productos de reacción fueron caracterizados mediante espectroscopia de infrarrojo y resonancia magnética nuclear hidrogeno y carbono 13.Ethinylestradiol is a common steroid in therapy and hormone regulation drugs and contains in its structure an alky negro up at carbon 17th at allows to carry out a[3+2] cycloaddition reaction to obtain 1, 2, 3 triazoles. In this work we describe an alternative methodology to obtain ethinylestradiol from estrone by means of a Grignard reaction us ingethylinylmagnesium bromide as nucleophile.This derivative was used as a synthon for the formation of a hybrid triazole composed of a steroid and a carbohydrate-derived azide (3-azide-1,2:5,6-diisopropylidene-α-D-glucofuranose) under classical thermal conditions. The reaction products were characterized by infrared spectroscopy, hydrogen and carbon 13 nuclear magnetic resonance

Síntesis de lactosa-triazol-teofilina

Es conocido, que la combinación de triazoles con un fragmento carbohidrato produce moléculas híbridas con potencial actividad biológica. En este trabajo se presenta el diseño y síntesis un nuevo glicoconjugado lactosa-1,2,3-triazol que contiene un fragmento de teofilina como sustituyente. Los triazoles fueron preparados fácilmente mediante una reacción de cicloadición [3 + 2] catalizada por un hidróxido doble laminar (HDL) de Cu/Al calcinado, empleando como materiales de partida la 1- azidolactosa y el derivado propargilado de la teofilina. Los nuevos híbridos carbohidrato-triazol-xantina fueron caracterizados por espectroscopía de infrarrojo (IR) y resonancia magnética nuclear de una y dos dimensiones (RMN).It is known that the combination of triazoles with a carbohydrate fragment produces hybrid molecules with potential biological activity. In this work, we present the design and synthesis of a new lactose-1,2,3-triazole glycoconjugate containing a theophylline moiety as a substituent. Triazoles were easily prepared by using a [3 + 2] cycloaddition reaction catalyzed by a calcined double laminar hydroxide (HDL) of Cu/Al, using 1-azidolactose and the propargylated derivatives of theophylline as starting material. The new carbohydrate-triazol-xanthine hybrids were adequately characterized by infrared (IR) spectroscopy and one- and two-dimensional nuclear magnetic resonance (NMR)

Complejos de paladio (II) con carbenos mesoiónicos (MICs) diversidad estructural y catálisis homogénea

Una nueva serie de mono- y bis-1,2,3-triazol-5-ilidenos de paladio(ii) conteniendo (MICs) han sido sintetizados, aislados y caracterizados. La introducción de paladio a sales de 1,2,3-triazolio mediante su reacción con Pd(OAc)₂ generó complejos bimetálicos del tipo [Pd(MIC)I₂]₂con puentes del tipo ( ₂-I₂)y también complejos monometálicos con estructuras generales [PdMIC₂I₂ como mezclas isoméricascis y trans. Adicionalmente, se realizó la síntesis selectiva de complejos tipo-PEPPSI [MIC(PdI₂)Py] mediante la reacción de las sales de triazolio con PdCl₂ y K₂CO₃ en piridina. Todos los compuestos han sido caracterizados mediante RMN de ¹H y ¹ᶾC, FT-IR y cristalografía de rayos-X de monocristal. Estudios catalíticos preliminares de los nuevos complejos en procesos de formación de enlaces C-C y C-N serán discutidos.A new series of mono- and bis-1,2,3-triazol-5-ylidene (MIC) palladium(ii) complexes have been synthesized, isolated and characterized. Palladation of N3-methylated phenoxy derived 1,2,3-triazolium salts withPd(OAc)₂,afforded ₂-I₂ bridged bimetallic [Pd(MIC)I₂]₂and monometallic biscarbene complexes PdMIC₂I₂as a mixture of cis- and trans isomers. Efficient synthesis of PEPPSI-type complexes [Py(PdI₂)MIC] was achieved by the treatment of the triazolium precursors with PdCl₂in pyridine. All the complexes have been fully characterized by ¹H and ¹ᶾC NMR, FT-IR and single crystal X-ray diffraction. Preliminary catalytic performances of the new complexes in C-C and C-N bond forming processes will be discussed