Fragmented areas due to agricultural activity: native vegetation dynamics at crop interface (Montecaseros, Mendoza, Argentina)

Plant communities fragmented by agricultural activities were analyzed in a 250-ha area in eastern plains of Montecaseros, Gral. San Martín Department, Mendoza, Argentina. A phytosociological method assessed different sites along a gradient of human intervention, from natural environments with no evidence of altered native vegetation to maximum farming modification, also including cleared and abandoned fields. Soil analyses supplemented the characterization of six plant communities. A scrubland physiognomy dominates the area, with species of the genera Larrea, Atriplex and Lycium. Tillage and crop abandonment can alter natural factors involved in soil formation, causing deterioration and exerting selective pressure on species colonizing these degraded environments. Evaluating natural vegetation before land clearing for agriculture is essential to assess, through species that indicate environmental conditions, edaphic limitations hindering crop establishment and affecting productivity. The conservation of natural communities on private lands destined for agriculture is valued. Highlights: This study aimed to characterize plant communities in natural and intervened environments, in a representative area of the fragmentation processes caused by agriculture in the Monte Province (Mendoza, Argentina). Plant biodiversity plays a strategic role in ecosystemic provision of goods and services necessary to human health and well-being. Cultivable land is a vulnerable and scarce resource, particularly in drylands, where ecosystems have low capacity for natural regeneration. Tillage and crop abandonment can alter natural factors involved in soil formation, causing deterioration and exerting selective pressure on species colonizing these degraded environments. In agricultural land, clearing can give rise to a mosaic of landscapes: productive crops merge with abandoned crops and fragments of natural fields. Evaluating natural vegetation before land clearing for agriculture is essential to assess, through species that indicate environmental conditions, edaphic limitations hindering crop establishment and affecting productivity. Studies of vegetation dynamism in private lands contribute to plan and implement sustainable land management, tending to recover and conserve biodiversity in degraded soils, considering all associated ecosystem services.Plant communities fragmented by agricultural activities were analyzed in a 250-ha area in eastern plains of Montecaseros, Gral. San Martín Department, Mendoza, Argentina. A phytosociological method assessed different sites along a gradient of human intervention, from natural environments with no evidence of altered native vegetation to maximum farming modification, also including cleared and abandoned fields. Soil analyses supplemented the characterization of six plant communities. A scrubland physiognomy dominates the area, with species of the genera Larrea, Atriplex and Lycium. Tillage and crop abandonment can alter natural factors involved in soil formation, causing deterioration and exerting selective pressure on species colonizing these degraded environments. Evaluating natural vegetation before land clearing for agriculture is essential to assess, through species that indicate environmental conditions, edaphic limitations hindering crop establishment and affecting productivity. The conservation of natural communities on private lands destined for agriculture is valued. Highlights: This study aimed to characterize plant communities in natural and intervened environments, in a representative area of the fragmentation processes caused by agriculture in the Monte Province (Mendoza, Argentina). Plant biodiversity plays a strategic role in ecosystemic provision of goods and services necessary to human health and well-being. Cultivable land is a vulnerable and scarce resource, particularly in drylands, where ecosystems have low capacity for natural regeneration. Tillage and crop abandonment can alter natural factors involved in soil formation, causing deterioration and exerting selective pressure on species colonizing these degraded environments. In agricultural land, clearing can give rise to a mosaic of landscapes: productive crops merge with abandoned crops and fragments of natural fields. Evaluating natural vegetation before land clearing for agriculture is essential to assess, through species that indicate environmental conditions, edaphic limitations hindering crop establishment and affecting productivity. Studies of vegetation dynamism in private lands contribute to plan and implement sustainable land management, tending to recover and conserve biodiversity in degraded soils, considering all associated ecosystem services.

Production and quenching of reactive oxygen species by pterin derivatives, an intriguing class of biomolecules

Pterins, a family of heterocyclic compounds derived from 2-aminopteridin-4(1H)-one, are widespread in living systems and participate in important biological functions, such as metabolic redox processes. Under UV-A excitation (320-400 nm), aromatic pterins (Pt) can generate reactive oxygen species (ROS), as a consequence of both energy-and electron-transfer processes from their triplet excited state. Quantum yields of singlet oxygen (1O2) production depend largely on the nature of the substituents on the pterin moiety and on the pH. Formation of the superoxide anion by electron transfer between the pterin radical anion and molecular oxygen leads to the production of significant amounts of hydrogen peroxide (H2O2) by disproportionation. Dihydropterins (H2Pt) do not produce 1O2 but are oxidized by this species with high rate constants yielding pterins as well as H2O2. In contrast to aromatic derivatives, H2Pt are oxidized by H2O2, and rates and products strongly depend on the nature of the substituents on the H2Pt moiety. Aromatic pterins have been found in vivo under pathological conditions, e.g., biopterin or 6-carboxypterin are present in the skin of patients affected by vitiligo, a depigmentation disorder. The biomedical implications of the production of ROS by pterin derivatives and their reactivity with these species are discussed.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Production and quenching of reactive oxygen species by pterin derivatives, an intriguing class of biomolecules

Pterins, a family of heterocyclic compounds derived from 2-aminopteridin-4(1H)-one, are widespread in living systems and participate in important biological functions, such as metabolic redox processes. Under UV-A excitation (320-400 nm), aromatic pterins (Pt) can generate reactive oxygen species (ROS), as a consequence of both energy-and electron-transfer processes from their triplet excited state. Quantum yields of singlet oxygen (1O2) production depend largely on the nature of the substituents on the pterin moiety and on the pH. Formation of the superoxide anion by electron transfer between the pterin radical anion and molecular oxygen leads to the production of significant amounts of hydrogen peroxide (H2O2) by disproportionation. Dihydropterins (H2Pt) do not produce 1O2 but are oxidized by this species with high rate constants yielding pterins as well as H2O2. In contrast to aromatic derivatives, H2Pt are oxidized by H2O2, and rates and products strongly depend on the nature of the substituents on the H2Pt moiety. Aromatic pterins have been found in vivo under pathological conditions, e.g., biopterin or 6-carboxypterin are present in the skin of patients affected by vitiligo, a depigmentation disorder. The biomedical implications of the production of ROS by pterin derivatives and their reactivity with these species are discussed.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Characterization β-carotene content of eight cultivars of carrot (Daucus carota L.) and its relation to the color

El objetivo fue determinar, durante dos años, el contenido de β-caroteno y su relación con el Índice de Color (IC), de ocho cultivares comerciales del tipo 'Flakkee' cultivadas en el INTA La Consulta. El diseño experimental a campo utilizado fue en bloques al azar con 3 repeticiones. Se evaluó β-caroteno (espectrofotometría a 450 nm) y se calculó el IC, mediante captación de imagen digital con PC y escáner, midiendo L, a y b del Sistema CIELAB. Los datos fueron analizados por ACP (análisis de componentes principales), la visualización de la variabilidad, por cartografiado de datos, análisis de varianza, pruebas de diferencia de medias y correlaciones. Los contenidos de β-carotenos y el IC de los cultivares se mantuvieron constantes durante los dos años estudiados, resultando las cultivares Natasha, Flakesse y Colmar las de mayor valor nutricional en cuanto a aporte de β-carotenos. En el rango de valores menores de 18 mg%g de β-carotenos, se observó una correlación positiva significativa en las cultivares Supreme, Spring y Laval. No se encontró una correlación alta lineal entre el IC y el contenido de β-carotenos. El uso del IC resulta adecuado para predecir, en un intervalo de valores, el contenido de β-carotenos en cultivares de zanahoria.The aim was to determine, eight commercial cultivars such as 'Flakkee' cultivated at INTA (National Institute of Agricultural Technology), Experimental Station La Consulta during two years, according to β-carotene content and its relationship with Color Index (CI). An experimental design with blocks at random with 3 replications was used. β-carotene was evaluated (spectrophotometry at 450 nm) and calculated the CI, by capture of digital image with PC and scanner, measuring L, a and b of CIELAB system. The results were analyzed by principal components analysis (PCA) and visualization of variability by mean of data mapping, analysis of variance, test of mean difference and correlations. The contents of β-carotene and the IC of cultivars remained constant during the two years studied, resulting Natasha, Flakesse and Colmar the ones with the greatest nutritional value in terms of contribution of β-carotene. In the range of values under 18 mg%g of β-carotene, we observed a significant positive correlation in the Supreme, Spring and Laval cultivars. It was found no significant high lineal correlation between the IC and β-carotene content. It is appropriate the use of color index to predict, in a range of values, β-carotene content in carrot cultivars.Fil: Ventrera, Nancy. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias Enológicas y AgroalimentariasFil: Vignoni, Lucía. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias Enológicas y AgroalimentariasFil: Alessandro, María Soledad. Instituto Nacional de Tecnología Agropecuaria (Argentina)Fil: Césari, Matilde. Universidad Tecnológica Nacional (Argentina). Facultad Regional MendozaFil: Césari, Ricardo Manuel. Universidad Nacional de Cuyo. Facultad de Artes y DiseñoFil: Guinle, Viviana. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias Enológicas y AgroalimentariasFil: Giménez, Adriana. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias Enológicas y AgroalimentariasFil: Tapia, Olga. Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias Enológicas y Agroalimentaria

Kinetic Control in the Regioselective Alkylation of Pterin Sensitizers: A Synthetic, Photochemical, and Theoretical Study

Alkylation patterns and excited-state properties of pterins were examined both experimentally and theoretically. 2D NMR spectroscopy was used to characterize the pterin derivatives, revealing undoubtedly that the decyl chains were coupled to either the O4 or N3 sites on the pterin. At a temperature of 70°C, the pterin alkylation regioselectively favored the O4 over the N3. The O4 was also favored when using solvents, in which the reactants had increased solubility, namely N,N-dimethylformamide and N,N-dimethylacetamide, rather than solvents in which the reactants had very low solubility (tetrahydrofuran and dichloromethane). Density functional theory (DFT) computed enthalpies correlate to regioselectivity being kinetically driven because the less stable O-isomer forms in higher yield than the more stable N-isomer. Once formed these compounds did not interconvert thermally or undergo a unimolecular ?walk? rearrangement. Mechanistic rationale for the factors underlying the regioselective alkylation of pterins is suggested, where kinetic rather than thermodynamic factors are key in the higher yield of the O-isomer. Computations also predicted greater solubility and reduced triplet state energetics thereby improving the properties of the alkylated pterins as 1 O 2 sensitizers. Insight on thermal and photostability of the alkylated pterins is also provided.Fil: Walalawela, Niluksha. City University of New York; Estados UnidosFil: Vignoni, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. City University of New York; Estados UnidosFil: Urrutia, María Noel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Belh, Sarah J.. City University of New York; Estados UnidosFil: Greer, Edyta M.. City University of New York; Estados UnidosFil: Thomas, Andrés Héctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Greer, Alexander. City University of New York; Estados Unido

A model to understand type I oxidations of biomolecules photosensitized by pterins

Photosensitized oxidations, in part responsible for the harmful effect of UV and visible radiation on biological systems, can take place through type I (generation of radicals) and type II (singlet oxygen) mechanisms. Pterins are heterocyclic compounds, widespread in living systems and involved in relevant biological functions. Pterins present a profuse and amazing photochemistry and are endogenous photosensitizers that act mainly via type I mechanism. This survey is aimed to contribute to a better understanding on the complex set of competitive pathways involved in type I photosensitization. Based on studies performed in model systems with pterins as photosensitizers, this review explores the mechanisms involved in the type I photooxidations of proteins, DNA and lipids sensitized by pterins. The generation of radicals and their subsequent reactions are described together with the analysis of the role of O 2 and reactive oxygen species. The chemical modification of pterins seeking for better properties and the effect of the photochemical processes at a cellular level are also analyzed.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Production and quenching of reactive oxygen species by pterin derivatives, an intriguing class of biomolecules

Pterins, a family of heterocyclic compounds derived from 2-aminopteridin-4(1H)-one, are widespread in living systems and participate in important biological functions, such as metabolic redox processes. Under UV-A excitation (320-400 nm), aromatic pterins (Pt) can generate reactive oxygen species (ROS), as a consequence of both energy-and electron-transfer processes from their triplet excited state. Quantum yields of singlet oxygen (1O2) production depend largely on the nature of the substituents on the pterin moiety and on the pH. Formation of the superoxide anion by electron transfer between the pterin radical anion and molecular oxygen leads to the production of significant amounts of hydrogen peroxide (H2O2) by disproportionation. Dihydropterins (H2Pt) do not produce 1O2 but are oxidized by this species with high rate constants yielding pterins as well as H2O2. In contrast to aromatic derivatives, H2Pt are oxidized by H2O2, and rates and products strongly depend on the nature of the substituents on the H2Pt moiety. Aromatic pterins have been found in vivo under pathological conditions, e.g., biopterin or 6-carboxypterin are present in the skin of patients affected by vitiligo, a depigmentation disorder. The biomedical implications of the production of ROS by pterin derivatives and their reactivity with these species are discussed.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Kinetic control in the regioselective alkylation of pterin sensitizers: a synthetic, photochemical, and theoretical study

Alkylation patterns and excited-state properties of pterins were examined both experimentally and theoretically. 2D NMR spectroscopy was used to characterize the pterin derivatives, revealing undoubtedly that the decyl chains were coupled to either the O4 or N3 sites on the pterin. At a temperature of 70°C, the pterin alkylation regioselectively favored the O4 over the N3. The O4 was also favored when using solvents, in which the reactants had increased solubility, namely N,N-dimethylformamide and N,N-dimethylacetamide, rather than solvents in which the reactants had very low solubility (tetrahydrofuran and dichloromethane). Density functional theory (DFT) computed enthalpies correlate to regioselectivity being kinetically driven because the less stable O-isomer forms in higher yield than the more stable N-isomer. Once formed these compounds did not interconvert thermally or undergo a unimolecular "walk" rearrangement. Mechanistic rationale for the factors underlying the regioselective alkylation of pterins is suggested, where kinetic rather than thermodynamic factors are key in the higher yield of the O-isomer. Computations also predicted greater solubility and reduced triplet state energetics thereby improving the properties of the alkylated pterins as 1 O2 sensitizers. Insight on thermal and photostability of the alkylated pterins is also provided.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Caracterización por contenido de β-carotenos de ocho cultivares de zanahoria (Daucus carota L.) y su relación con el color

The aim was to determine, eight commercial cultivars such as 'Flakkee' cultivated at INTA (National Institute of Agricultural Technology), Experimental Station La Consulta during two years, according to β-carotene content and its relationship with Color Index (CI). An experimental design with blocks at random with 3 replications was used. β-carotene was evaluated (spectrophotometry at 450 nm) and calculated the CI, by capture of digital image with PC and scanner, measuring L, a and b of CIELAB system. The results were analyzed by principal components analysis (PCA) and visualization of variability by mean of data mapping, analysis of variance, test of mean difference and correlations. The contents of β-carotene and the IC of cultivars remained constant during the two years studied, resulting Natasha, Flakesse and Colmar the ones with the greatest nutritional value in terms of contribution of β-carotene. In the range of values under 18 mg%g of β-carotene, we observed a significant positive correlation in the Supreme, Spring and Laval cultivars. It was found no significant high lineal correlation between the IC and β-carotene content. It is appropriate the use of color index to predict, in a range of values, β-carotene content in carrot cultivars.El objetivo fue determinar, durante dos años, el contenido de β-caroteno y su relación con el Índice de Color (IC), de ocho cultivares comerciales del tipo 'Flakkee' cultivadas en el INTA La Consulta. El diseño experimental a campo utilizado fue en bloques al azar con 3 repeticiones. Se evaluó β-caroteno (espectrofotometría a 450 nm) y se calculó el IC, mediante captación de imagen digital con PC y escáner, midiendo L, a y b del Sistema CIELAB. Los datos fueron analizados por ACP (análisis de componentes principales), la visualización de la variabilidad, por cartografiado de datos, análisis de varianza, pruebas de diferencia de medias y correlaciones. Los contenidos de β-carotenos y el IC de los cultivares se mantuvieron constantes durante los dos años estudiados, resultando las cultivares Natasha, Flakesse y Colmar las de mayor valor nutricional en cuanto a aporte de β-carotenos. En el rango de valores menores de 18 mg%g de β-carotenos, se observó una correlación positiva significativa en las cultivares Supreme, Spring y Laval. No se encontró una correlación alta lineal entre el IC y el contenido de β-carotenos. El uso del IC resulta adecuado para predecir, en un intervalo de valores, el contenido de β-carotenos en cultivares de zanahoria

El uso de parámetros magnéticos en estudios paleolimnológicos en Antártida

En esta contribución se describen las distintas técnicas y mediciones magnéticas utilizadas en Magnetismo Ambiental y Paleomagnetismo. Tales mediciones ofrecen útiles indicadores para realizar estudios relacionados con cambios climáticos y ambientales, así como herramientas de datación. Si bien es ampliamente conocida la utilidad de la susceptibilidad magnética, en primer lugar se discute el potencial y necesidad del uso de parámetros adicionales obtenidos a partir de mediciones de magnetizaciones remanentes (natural, anhistérica e isotérmica), histéresis magnética y estudios termomagnéticos. A continuación se presentan resultados magnéticos obtenidos en sedimentos lacustres del Archipiélago James Ross (NE de la Península Antártica) como un caso de estudio. Se complementa con estudios sedimentológicos, hidroquímicos, geoquímicos y de estadística multivariada, pero se pone énfasis en los parámetros magnéticos y su relación con los distintos procesos que ocurren en los sistemas lacustres antárticos. Se analiza además el uso de las paleointensidades relativas como herramienta de datación en lagunas antárticas