Prebiotic peptide elongation by the chemoselective ligation of aminonitriles

Elucidating the sequence of events that led to the emergence of life on Earth remains one of the most fundamental open problems in all of science. At its core, a living system requires a substrate able to store, replicate and modify information. Due to its ability to serve both as a genetic information carrier and biocatalyst, RNA was first proposed to be sufficient. However, decades of efforts have failed to overcome the difficulties met when attempting to experimentally realise pure RNA models. A recent development was the proposal of a hybrid peptide-RNA world, which would tap into the enzymatic and structural capacity of peptides to complement the properties of RNA. While promising, this hypothesis found itself limited by similar hurdles. Chiefly, the formation of peptide bonds under prebiotic conditions remains a daunting challenge. Although amides are arguably the most important chemical group in all of biology and synthetic chemistry, their formation remains infamously difficult. These difficulties are compounded by the specificities of the prebiotic environment, which mandates that amidations happen in water, and precludes the use of sophisticated synthetic reagents. Due to its biomimetic nature and the assumed prebiotic abundance of amino acid monomers, the field has traditionally focused on the free polymerisation of amino acids. However, all documented amino acid-based strategies have failed to produce sufficient amounts of peptides, and are limited to a small subset of the proteinogenic amino acids. This work marks a clear departure from such paradigms, and sets out to explore the reactivity of aminonitrile precursors to amino acids. Herein, we demonstrate that (i) aminonitriles can be converted to N-capped peptide thioacids and aminothioacids; (ii) those thioacids chemoselectively ligate with aminonitriles to afford proteinogenic structures; (iii) this methodology can operate as a continuous, one-pot elongation cycle, which affords N-capped peptides in unprecedentedly high yields. Those findings bring to light a direct link between prebiotic protometabolism and the canonical peptide structures of extant biology, and pave the way towards the experimental realisation of hybrid protein-RNA protobiological systems

Abundance, movement and habitat use of Swainson's hawks in their wintering grounds, Argentina

Tesis para obtener el grado de Master of Science, de la University of Florida, en 2000Knowledge of habitat use by a particular species is necessary in developing species conservation plans. Large-scale mortality of Swainson’s hawks (Buteo swainsoni) in Argentina during austral summer 1995-96 identified the need to address several questions about relationships between hawks and their wintering ground environment. In 1996, an international and interdisciplinary research project involving numerous institutions and agencies was initiated to understand causes of Swainson’s hawk mortality and to prevent future mortality events. A research component addressed questions about the patterns of abundance; movement and habitat use of Swainson’s hawks in particular wintering areas. In this study, population abundances, individual movements and habitat use, both at population and individual levels of resolution, were analyzed at a landscape scale in two study areas. These areas were located in La Pampa and Santa Fe provinces of Argentina and the study was conducted in 1996-97 and 1997-98 austral summers. Field methods included systematic surveys, conventional radio tagging of individual hawks and focal observations. Densities of hawks varied between 4.40 and 5.02 hawks/km2 in La Pampa and 3.51 hawk/km2 in Santa Fe, with high variations in these values through the season. Hawks widely dispersed at regional level (far away from the limits of the study area) and used a defined study area with a random pattern, without constituting tight groups or flocks. Finally, both at population and individual levels, hawks selected permanent pastures (for foraging), plowed fields (for sunbathing/resting and sometimes for foraging) and woodlands (for roosting), but their clustered spatial distribution was not associated with the abundance of these selected habitat types. These results reflected similarities in the pattern of habitat use with the breeding areas, and they could be expected from adaptations of a migratory raptor to the dynamic changes of heterogeneous agricultural landscapes, especially in relation to food availability. Patterns of habitat use showed a combination of risk factors that made hawks susceptible to pesticide applications in their wintering ground. In addition, values of population abundance found in this study as well as patterns of movement gave a baseline for the development of conservation measures directed to explore and prevent the incidence of agricultural practices, such as pesticide applications and changes in land use, on populations of Swainson’s hawks wintering in the Argentinean pampas.EEA ParanáFil: Canavelli, Sonia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; Argentin

Ecological and Human Dimensions of the Monk Parakeet Damage to Crops in Argentina

Tesis para obtener el grado de Doctor of Philosophy, de la University of Florida (Estados Unidos), en 2011The Monk Parakeet (Myiopsitta monachus) is considered among the most important bird pest species causing damage to crops in Argentina. In this study, I explored habitat features influencing abundance and damage of monk parakeets to crop fields and density of nests in inhabited farms with eucalyptus trees at multiple spatial levels. Additionally, I examined socio-psychological and socio-demographic factors influencing farmers´ preferences about management of monk parakeet damage to crops. Monk parakeet abundance and damage was greater in sunflower than in corn fields. Landscape variables, such as distance to nearest sites with trees, percentage of landscape with trees, and availability of foraging sites for monk parakeets around the crop fields, were more important than local variables in explaining monk parakeet damage to crop fields. However, local variables, such as field area, plant density and percentage of field border with trees, also were related to damage. Conversely, the density of monk parakeet nests in inhabited farms with eucalyptus trees was not clearly explained by any variable or combination of variables modeled in this study. Farmers preferred population control strategies, such as nest destruction and killing of birds, for decreasing monk parakeet damage to crops. Preferences of farmers for management strategies were related more strongly to attitudes toward monk parakeets than to any other factor considered in this study. Other important sociopsychological factors were perceived efficacy and previous knowledge about management strategies. Perceptions of magnitude of damage by monk parakeets practically were not related to preferences. Socio-demographic factors, such as age and education, were related to preferences in different ways depending on the management strategy. Based on this study, managers should consider both local and landscape factors when planning management measures to prevent monk parakeet damage to crop and reduce nesting on farms. Additionally, extension actions should be oriented to modifying attitudes toward monk parakeets as well as communicating and showing the efficacy of alternative management strategies. Given the current uncertainties in the outcome of management actions, an adaptive management approach would be useful to evaluate the efficacy of strategies other than lethal or reproductive control.EEA ParanáFil: Canavelli, Sonia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; Argentin

Manejo del daño por cotorras en frutales

Las "cotorras” o “catas" pueden ocasionar daños en flores, brotes y frutos en crecimiento o maduros de frutales de pepita, carozo y frutos secos.EEA Alto ValleFil: Canavelli, Sonia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; Argentin

Educación en Tecnología y Matemática en Criptografía : Puntos de encuentro

En este artículo narramos la experiencia vivida, trabajando en la búsqueda de puntos de encuentro entre la Matemática y la Informática que permitan articular a su vez la Escuela Media con la Universidad. Las actividades se desarrollaron en el marco del Proyecto denominado “Universidad-Escuela Media: una complejidad para compartir II”, implementado por la Secretaría Académica de la Universidad Nacional de Entre Ríos junto con el Consejo General de Educación de dicha provincia, durante el año 2004. Se puso el énfasis en la “Teoría Elemental de Números”. Temas básicos de esta parte de la Matemática son los siguientes: Divisibilidad. Sistemas de numeración. Máximo común divisor. Algoritmo de Euclides. Números Primos. Teorema fundamental de la Aritmética. Congruencias. Congruencias con incógnitas. El teorema chino del resto. El pequeño teorema de Fermat. El teorema de Euler-Fermat. Estos temas no siempre reciben en la Escuela la atención que merecen. Nos referimos a los niveles tanto elemental como medio. Esta situación debe corregirse, pues la Aritmética posee una extensa tradición histórica y es hoy una herramienta fundamental en el dinámico campo de las Tecnologías de la Información (podemos decir que todos los temas enunciados precedentemente intervienen para explicar uno de los sistemas más utilizados hoy para cifrar mensajes, el llamado sistema RSA en honor a sus creadores: Rivest, Shamir y Adleman).Red de Universidades con Carreras en Informática (RedUNCI

Educación en Tecnología y Matemática en Criptografía : Puntos de encuentro

En este artículo narramos la experiencia vivida, trabajando en la búsqueda de puntos de encuentro entre la Matemática y la Informática que permitan articular a su vez la Escuela Media con la Universidad. Las actividades se desarrollaron en el marco del Proyecto denominado “Universidad-Escuela Media: una complejidad para compartir II”, implementado por la Secretaría Académica de la Universidad Nacional de Entre Ríos junto con el Consejo General de Educación de dicha provincia, durante el año 2004. Se puso el énfasis en la “Teoría Elemental de Números”. Temas básicos de esta parte de la Matemática son los siguientes: Divisibilidad. Sistemas de numeración. Máximo común divisor. Algoritmo de Euclides. Números Primos. Teorema fundamental de la Aritmética. Congruencias. Congruencias con incógnitas. El teorema chino del resto. El pequeño teorema de Fermat. El teorema de Euler-Fermat. Estos temas no siempre reciben en la Escuela la atención que merecen. Nos referimos a los niveles tanto elemental como medio. Esta situación debe corregirse, pues la Aritmética posee una extensa tradición histórica y es hoy una herramienta fundamental en el dinámico campo de las Tecnologías de la Información (podemos decir que todos los temas enunciados precedentemente intervienen para explicar uno de los sistemas más utilizados hoy para cifrar mensajes, el llamado sistema RSA en honor a sus creadores: Rivest, Shamir y Adleman).Red de Universidades con Carreras en Informática (RedUNCI

A mild TCEP-based para-azidobenzyl cleavage strategy to transform reversible cysteine thiol labelling reagents into irreversible conjugates

It has recently emerged that the succinimide linkage of a maleimide thiol addition product is fragile, which is a major issue in fields where thiol functionalisation needs to be robust. Herein we deliver a strategy that generates selective cysteine thiol labelling reagents, which are stable to hydrolysis and thiol exchange

Considerations for reducing conflicts around damage of agricultural crops by Monk Parakeet (Myiopsitta monachus)

La Cotorra (Myiopsitta monachus) está considerada entre las principales especies de aves que causan daños en cultivos agrícolas en Argentina. Históricamente, se ha favorecido el control letal como método más efectivo para disminuir los daños. No obstante, existen cada vez más cuestionamientos a esta práctica. En este trabajo se resumen los problemas que involucran a la Cotorra y las actividades agrícolas, incluyendo características de los daños y aspectos ecológicos y humanos que favorecerían los conflictos originados por los daños en los cultivos. Además, se presenta un compendio de las alternativas de manejo actualmente disponibles para disminuir los daños. Si bien existen características ecológicas de las cotorras que favorecerían los daños en determinadas situaciones, hay factores humanos, incluyendo la sobreestimación de los daños y la tendencia a usar métodos de control poblacional (letal y reproductivo), que probablemente contribuyan a generar un nivel de conflicto mayor del que realmente existe. Esto sería favorecido por la casi inexistencia de estimaciones independientes de las pérdidas ocasionadas por las cotorras, lo que dificulta una evaluación objetiva del problema. A fin de contribuir a una agricultura más sustentable, se considera perentorio explorar enfoques de manejo estratégico, desarrollando investigaciones multidisciplinarias tendientes a identificar claramente los conflictos, cuantificar la magnitud de los daños, aplicar alternativas de manejo adecuadas a cada situación y, finalmente, evaluar objetivamente los resultados, en términos de costo–beneficio.The Monk Parakeet (Myiopsitta monachus) is considered among the most damaging bird pest species for crops in Argentina. Historically, lethal control has been preferred as the most effective method to decrease damage. However, objections to this method are increasing. We summarize problems involving parakeets and crop production, including crop damage characterization as well as ecological and human aspects involved in the conflicts. Additionally, we summarize available management alternatives to decrease crop damage. Although certain ecological characteristics of the Monk Parakeet would favour crop damage in some situations, human factors, such as damage overestimation and tendency to use population control methods (lethal and reproductive), probably contribute to a magnification of the dimensions of the conflict. This also will be favoured by the practically inexistent damage estimations on crops, making an objective evaluation of conflicts difficult. In order to develop a more sustainable agriculture, we urge the application of strategic management principles, with the development of multidisciplinary research to clearly identify conflicts, quantify the magnitude of damage, apply management alternatives appropriate for each situation and, finally, objectively evaluate the results in terms of costs and benefits

Anidamiento de paloma torcaza (Zenaida auriculata) en rastrojos de sorgo

La paloma torcaza (Zenaida auriculata) es una de las especies de aves más co-munes y abundantes de Argentina, con gran capacidad de adaptación a los am-bientes modificados por el hombre. Un aspecto clave del éxito de esta especiees su capacidad para anidar de manera colonial en remanentes de bosque enpaisajes agrícolas. Este factor ha contribuido significativamente al crecimientopoblacional experimentado por la especie en las últimas décadas. Se presentael hallazgo de una nidada colonial en rastrojos de sorgo. En octubre de 2013 selocalizó una colonia de anidamiento de paloma torcaza en un lote con rastrojosde sorgo. En dicho lote, se realizaron 5 transectas de faja. Se obtuvo un promediode 0,89 nidos (±0,19) por m 2 y 1,79 (±0,17), huevos por nido. La mayoría (93,4 %)de los huevos estaba sano y el resto (6,6 %) mostraba signos de depredación.Éste sería el primer registro publicado de anidamiento colonial de torcaza enrastrojos de cultivo de sorgo. Establecer la frecuencia de este comportamientode anidamiento a escala regional y estimar el impacto que podría tener sobre elcrecimiento poblacional de esta especie sería importante para comprender, demanera más cabal, los aumentos poblacionales experimentados por esta palomaen los últimos años.Eared dove (Zenaida auriculata) is one of the most common and most abundant bird species in Argentina. Eared doves are highly adaptable to human–modified environments. A key aspect of the success of this species is its ability for colonial breeding in forest patches in agricultural landscapes. This factor has contributed significantly to the population growth experienced by the species in recent de-cades. A finding of colonial breeding in sorghum stubble is presented. In Octo-ber 2013 a breeding colony of eared doves was located on a plot with sorghum stubble. In this plot, five belt–transects were set for counting nests and eggs. An average of 0.89 nests (±0.19) per m2 was obtained. The average number of eggs per nest was 1.79, of which 93.4 % were intact and 6.6 % were damaged, with signs of predation. This study constitutes the first published record of Eared doves nesting colonially in sorghum stubble fields. It would be important to esti-mate, at regional scale, how frequent this nesting behavior is, and to estimate the impact this might have on the population growth of this species in recent years.EEA ParanáFil: Dardanelli, Sebastian. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; ArgentinaFil: Addy Orduna, Laura. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; ArgentinaFil: Canavelli, Sonia Beatriz. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Paraná; Argentin