Examinando DD. Ciencias Naturales por Fecha
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- PublicaciónAcceso abiertoFactores de riesgo psicosociales y ambientales asociados a trastornos mentales(2010-06) Londoño, Nora Helena; Marín, Carlos A.; Juarez, Fernando; Palacio Sañudo, Jorge Enrique; Muñiz, Oscar; Escobar, Blanca; Herrón, Isabel; Agudelo, Diana; Lemos, Mariantonia; Toro, Beatriz E.; Ochoa, Nohora L.; Hurtado, Maria Hortensia; Gómez, Yvonne; Uribe Rodríguez, Ana Fernanda; Rojas, Alba Luz; Pinilla, Mónica Liliana; Villa Roel, Diana; Villegas, Martha Juliana; Arango, Ana Lucía; Restrepo García, Paula Andrea; López, Isabel CristinaIn Colombia, there are few studies on the association of psychosocial and environmental factors with the most prevalent mental disorders; such studies are important due to the context of violence, social insecurity, and job and economic instability in the country. The objective of this study was to identify the psychosocial and environmental risk factors for mental disorders, in users of psychological services in Colombia. The Mini International Neuropsychiatric Interview and a Questionnaire to evaluate the Axis-IV of the DSM-IV-TR were applied to 490 participants. The analysis comprised descriptive statistics and risk factors. As risk factors for depression, there were identified housing problems, access to health care services, problems related to the primary group, economics, problems of the social environment, and labor. For generalized anxiety, there were identified economic and education issues. For panic disorders, the risk factors were related to social environment, and for social phobia, the risk factors were problems in education, work and social environment.
- PublicaciónAcceso abiertoParticipation of valine 171 in α-helix 5 of Bacillus thuringiensis Cry1Ab δ-endotoxin in translocation of toxin into Lymantria dispar midgut membranes(2010-10-01) Alzate, Oscar; Osorio, Cristina; Florez, Alvaro M.; Dean, Donald H.The Cry1Ab δ-endotoxin V171C mutant protein exhibits a 25-fold increase in toxicity against Lymantria dispar, which correlates with a faster rate of partitioning into the midgut membrane and slightly decreased protein stability. This is an insect-specific mechanism; similar results were not observed in Manduca sexta, another Cry1Ab δ-endotoxin-susceptible insect.
- PublicaciónAcceso abiertoBacteria del Lago Mono propone paradigmas adicionales a la Biología Moderna(2011-03) Florez, Alvaro M.; Quijano, Jairo; Orduz, Sergio
- PublicaciónAcceso abiertoLa narrativa psicopatológica desde el enfoque de la complejidad(2011-07) Álvarez Ramírez, Leonardo YovanyIn postmodern age, the language and the narration have become into the base of the psychotherapeutic intervention, however, the relationships between them and the way, individuals structure and define their behaviors, beliefs, feelings and interactions has been done since a focus based on values of harmony, prediction and perfection, which belong to modern sciences. Objective: Positing how the reality since the people builds their emotional health should be understand from another and complementary values like contradiction, blurring, impredictiveness, uncertainty (complexity model components). Materials and methods: Hermeneutic is used to the analysis through Discussion: That mental health intervention from a narration intervention implies reckoning the individual´s behavior as a complex reality.
- PublicaciónAcceso abiertoEl debate axiológico como propuesta de intervención terapéutica complementaria a los debates clásicos de la REBT, en la depresión.(2011-07) Álvarez Ramírez, Leonardo YovanyThis study was aimed to establish a differential effect that facilitates reduction of depressive symptoms of the axiological argument administrated in conjunction with the logical, empirical and pragmatic of the REBT, to an experimental group of 20 masculine adult patients, depressed diagnosed, versus another equivalent group of control in which only seconds were administrated. 15 sessions were conducted by two therapists, and strategies of argument were used. The improvement effects in the experimental participants are confirmed by the chi-square results and they are reported on the Beck scale with a value of X2=6,97534, higher than the expected with X2= 3,551with p≤0.001 and fg=32. It is concluded, the axiological argument promotes additional evaluative-emotional operations such as ranking, reassessment, comparison, and reformulation of principles and values from a possibilistic, probabilistic, relativistic, and elective view that makes flexible the patient's philosophy and decreases their depressive symptoms.
- PublicaciónAcceso abiertoCharacterization of a mutant bacillus thuringiensis delta endotoxin with enhanced stability and toxicity(2011-10) Hussain, Syed-Rehan A.; Florez, Alvaro M.; Osorio, Cristina; Dean, Donald H.; Alzate, OscarThe centrally located a-helix 5 of Bacillus thuringiensis d-endotoxins is critical for insect toxicity through ion-channel formation. We analyzed the role of the highly conserved residue Histidine 168 (H168) using molecular biology, electrophysiology and biophysical techniques. Toxin H168R was ~3-fold more toxic than the wild type (wt) protein whereas H168Q was 3 times less toxic against Manduca sexta. Spectroscopic analysis revealed that the H168Q and H168R mutations did not produce gross structural alterations, and that H168R (Tm= 59 °C) was more stable than H168Q (Tm= 57.5 °C) or than the wt (Tm= 56 °C) toxins. These three toxins had similar binding affinities for larval midgut vesicles (Kcom) suggesting that the differences in toxicity did not result from changes in initial receptor binding. Dissociation binding assays and voltage clamping analysis suggest that the reduced toxicity of the H168Q toxin may result from reduced insertion and/or ion channel formation. In contrast, the H168R toxin had a greater inhibition of the short circuit current than the wt toxin and an increased rate of irreversible binding (kobs), consistent with its lower LC50 value. Molecular modeling analysis suggested that both the H168Q and H168R toxins could form additional hydrogen bonds that could account for their greater thermal stability. In addition to this, it is likely that H168R has an extra positive charge exposed to the surface which could increase its rate of insertion into susceptible membranes.
- PublicaciónAcceso abiertoEvaluación de acaricidas para el control de garrapatas (riphicephalus (Boophilus) microplus) que afectan al ganado bovino de doble propósito usando modelos lineales generalizados(2011-10-06) González, A.; Tapias, D.; Pérez, M.; Carvajalino, M.; Velandia, D.; Borges, R.In this paper, we present the results of an evaluation of several chemicalproducts used as acaricides: alpha-cypermethrin Amitraz, Cypermethrin, andEthion over the control of Rhipicephalus (Boophilus) microplus that affects thedouble purpose bovines. Tics (Rhipicephalusmicroplus) were collected in twoproduction units in each County of the Municipality of Colón, in the Zulia Statein Venezuela. After a selection of comparable insects, they were immersed inconcentrations obtained from the recommended dose and concentration of theacaricides of each active principle. Then, the experiment was followed until thelarvaes hatching and the number of death and alive ones larva was counted ineach case. The data was analyzed using techniques related to Generalized LinearModels, considering first, binary models of dose-response based on the binomialdistribution to model the proportion of death larva for each concentration, usingmodels for each acaricide and, the “best” model was selected using the deviancesand information criteria, considering the Akaike criteria (AIC) the Pearson χ2,the deviance and a adaptation of the R2 for binomial model. After determining thebest performance concentration of each acaricide, it was performed an analysis ofcontingency tables using a Poisson distribution to compare the effect of theacaricides, using in this case the recommended dose for each product.
- PublicaciónAcceso abiertoCalidad microbiológica de alimentos remitidos a un laboratorio de salud pública en el año 2009(2011-11) Blanco Ríos, Freddy A.; Casadiego Ardila, Gloria; Pacheco, Paola A.Objective Testing the microbiological quality of food samples from municipalities in the Santander department which were processed by the Public Health Laboratory (PHL) in 2009. Materials and Methods The microbiological quality of food samples sent to the Santander PHL in 2009 was analysed by collecting reports issued by the institution and conducting a statistical analysis of 763 food samples from 76 municipalities in the department. Minitab statistical software (version 15) and Statistica (version 8.0) were used for analysing the information by municipality; this information was organised by food category and adverse incident frequency was analysed in each municipality from January to December 2009. Results It was seen that 45.2 % (n=345) of 763 food records had bacterial contamination; there was a greater frequency of these events in the municipalities of Barichara, Barrancabermeja, Floridablanca, Girón, Socorro and Valle de San Jose accounting for 33.6 % (n=116) of all affected samples. The main foods that had non-standard parameters were prepared foods (160 samples submitted), of which 80 had alterations in quality (50 %), followed by drinks like fruit juice and soft drinks (48.3 %), dairy products (47.9 %) and meat (40.7 %). Conclusions A high rate of food contamination was found in the samples sent to PHL during 2009; this information is useful for planning preventative action within the ongoing PHL surveillance programme.
- PublicaciónAcceso abiertoOntogenia de los estróbilos, desarrollo de los esporangios y esporogénesis de equisetum giganteum (Equisetaceae) en los Andes de Colombia(2011-12) Rincón Barón, Edgar Javier; Forero Ballesteros, Helkin Giovani; Gélvez Landazábal, Leidy Viviana; Torres, Gerardo Andrés; Rolleri, Cristina HildaOntogeny of strobili, sporangia development and sporogenesis in Equisetum giganteum (Equisetaceae) from the Colombian Andes. Studies on the ontogeny of the strobilus, sporangium and reproductive biology of this group of ferns are scarce. Here we describe the ontogeny of the strobilus and sporangia, and the process of sporogenesis using specimens of E. giganteum from Colombia collected along the Rio Frio, Distrito de Sevilla, Piedecuesta, Santander, at 2 200m altitude. The strobili in different stages of development were fixed, dehydrated, embedded in paraffin, sectioned using a rotatory microtome and stained with the safranin O and fast green technique. Observations were made using differential interference contrast microscopy (DIC) or Nomarski microscopy, an optical microscopy illumination technique that enhances the contrast in unstained, transparent. Strobili arise and begin to develop in the apical meristems of the main axis and lateral branches, with no significant differences in the ontogeny of strobili of one or other axis. Successive processes of cell division and differentiation lead to the growth of the strobilus and the formation of sporangiophores. These are formed by the scutellum, the manubrium or pedicel-like, basal part of the sporangiophore, and initial cells of sporangium, which differentiate to form the sporangium wall, the sporocytes and the tapetum. There is not formation of a characteristic arquesporium, as sporocytes quickly undergo meiosis originating tetrads of spores. The tapetum retains its histological integrity, but subsequently the cell walls break down and form a plasmodium that invades the sporangial cavity, partially surrounding the tetrads, and then the spores. Towards the end of the sporogenesis the tapetum disintegrates leaving spores with elaters free within the sporangial cavity. Two layers finally form the sporangium wall: the sporangium wall itself, with thickened, lignified cell walls and an underlying pyknotic layer. The mature spores are chlorofilous, morphologically similar and have exospore, a thin perispore and two elaters. This study of the ontogeny of the spore-producing structures and spores is the first contribution of this type for a tropical species of the genus. Fluorescence microscopy indicates that elaters and the wall of the sporangium are autofluorescent, while other structures induced fluorescence emitted by the fluorescent dye safranin O. The results were also discussed in relation to what is known so far for other species of Equisetum, suggesting that ontogenetic processes and structure of characters sporoderm are relatively constant in Equisetum, which implies important diagnostic value in the taxonomy of the group.
- PublicaciónAcceso abiertoDesarrollos preliminares de la escala de motivación (EM1) para adultos basada en el modelo motivacional de Mc Clelland.(2012-01) Álvarez Ramírez, Leonardo YovanyEl objetivo del presente estudio fue diseñar una escala preliminar diferenciada e integrada de las dimensiones motivacionales de poder, logro, filiación y reconocimiento en población adulta según el modelo de las motivaciones sociales de Mc Clelland, estableciendo sus correlaciones con la edad, el estrato socioeconómico, nivel educativo de los participantes y las diferencias según el sexo. El repertorio de ítems de la escala fue evaluado por jueces expertos y piloteado en grupos equivalentes a la muestra objetivo. Los datos obtenidos en esta se sometieron a análisis de componentes principales por rotación varimax y correlacional interfactores así como validación externa con el CMT (Cuestionario de Motivación para el Trabajo) y el MPS (Escala de motivaciones Psicosociales). Los resultados arrojaron una solución de cuatro factores: motivación de logro, de poder, filiativa y de reconocimiento. Las correlaciones con el CMT y el MPS, para su validez, fueron positivas y considerables (r=0.75 y r=0.79) y la estabilidad en el retest mostró coeficientes Alfa Cronchbach buenos (α= 0.64 y α=0.87). Las correlaciones con la edad (0.55≤ r≤0.61), el nivel educativo (0.60≤η≤0.69) y el estrato (0.48≤η≤0.71), fueron apenas promedio y las diferencias por sexo no significativas con p< 0.0344.Se concluye que el EM1 es preliminarmente un buen candidato a instrumento tipo escala para evaluar las motivaciones psicosociales de logro, poder, afiliación y reconocimiento en adultos.
- PublicaciónAcceso abiertoTwo disulfide mutants in domain I of Bacillus thuringiensis Cry3Aa δ-endotoxin increase stability with no effect on toxicity(2012-05) Wu, Sheng Jiun; Florez, Alvaro M.; Homoelle, Bradley J.; Dean, Donald H.; Alzate, OscarTo increase protein stability and test protein function, three double-cysteine mutations were individually introduced by protein engineering into the cysteinefree Cry3Aa δ-endotoxin from Bacillus thuringiensis. These mutations were designed to create disulfide bonds between α-helices 2 and 5 (positions 110 - 193), and α-helices 5 and 7 (positions 195 - 276 and 198 - 276). Comparison of the CD spectra of the wild-type and the double-cysteine mutant proteins indicates a tighter helical packing consistent with formation of at least two of the disulfide bonds between the central and the outer helices. Thermal stability analysis indicates that potential covalent linkages between the central α-helix 5 and the other helices increase resistance to thermal denaturation by 10˚C to 14˚C compared to the thermal stability of the wild-type protein. Spectroscopic analysis of the disulfide-specific absorbance band indicates that the double mutant proteins are more stable to temperature and denaturant (guanidine hydrochloride) than the wild-type protein, as a result of the formation of two of the disulfide bridges. These results indicate that the double mutations M110C/F193C and A198C/V276C successfully established disulfide bonds, resulting in a more stable structure of the entire toxin. Despite the increase in stability and structural changes introduced by the disulfide bonds, no effect on toxicity was observed. A possible mechanism involving the insertion of all of domain I of Cry3Aa toxin into the target membrane accounts for these observations.
- PublicaciónAcceso abiertoSimbiosis micorrízica arbuscular y acumulación de aluminio en brachiaria decumbens y manihot esculenta(2012-07) Guerra Sierra, Beatriz Elena; Chacón, Martha RocioOil palm (Elaeis guineensis Jacq) soils from-Santander Puerto Wilches-Colombia, have low fertility, high aluminum saturation and low density of mycorrhizal fungal spores. Behavior mycorrhizal symbiosis was evaluated XVLQJ QDWLYH VRLOV ZLWK P\FRUUKL]DH 0$ DQG VWHULOH VRLOV ZLWKRXW mycorrhizae (MA -) using Brachiaria decumbens and Manihot esculenta, both plants have high mycotrophy and ion binding capacity of aluminum. Variables were spore density, percentage of mycorrhizal colonization, biomass and root length, concentration of aluminum at leaf and root. Was performed (ANOVA) with a two-way general linear model. There were mycorrhizal colonization rates exceeding 70% in B. decumbens in soils with concentrations of 0,6 and 1,4 meq/100 g of aluminum. M. esculenta establishedmycorrhizationat 50% in all four soils. Spores were increased up to 200% in the two hosts plants. Aluminum concentrations were higher in mycorrhizal roots, while leaf-level values were lower.
- PublicaciónAcceso abiertoAplicación de la metodología de series de tiempo en la estimación de los niveles de exportación de café de Colombia periodo 1958-2011(2013-08-14) Pérez Pulido, Miguel-Oswaldo; Orlandoni-Merli, Giampaolo; Ramoni Perazzi, JosefaUn elemento fundamental para el sector cafetero colombiano, es saber a corto, mediano y largo plazo, el comportamiento de las exportaciones de café suave de Colombia, para conocer su relación en los procesos de ventas y producción. En concordancia con lo anterior, se realizó una evaluación de los niveles de exportaciones de café, en forma mensual desde inicios de 1958 hasta finales de 2008. Con el objetivo de desarrollar un modelo que permita caracterizar y obtener pronósticos sobre el comportamiento de las exportaciones de café realizadas en el país; para ello, se usó la metodología Box Jenkins, siguiendo las fases para los modelos ARIMA (Autoregresivo Integrado de Media Móvil). Los datos fueron tomados de la página web de la Federación Nacional de Cafeteros de Colombia. La serie bajo estudio mostró un comportamiento estacional, donde los primeros trimestres presentan los menores niveles del año, particularmente en febrero, mes que registra los niveles más bajos de exportaciones del año, estos niveles trimestralmente van incrementándose de forma paulatina hasta alcanzar el mayor nivel de exportaciones en el IV trimestre, específicamente entre Noviembre y Diciembre. Finalmente se obtuvieron los pronósticos entre los años 2009 y 2011, siguiendo un comportamiento estable respecto al periodo de validación de la muestra de la serie. Los datos fueron analizados utilizando el lenguaje R -PROJECT v 11.0.
- PublicaciónAcceso abiertoIndigenous arbuscular mycorrhizal fungi in oil palm soils in Colombia(2013-09) Guerra Sierra, Beatriz Elena; Serge, Sokolski; Dion, PatriceGenerally monocultures have replaced tropical forests and other ecosystems, causing big changes and little is known about the influence of the practice of monoculture in density and biodiversity of mycorrhizal fungi (AMF) species. Spore production is highly depend of physiologycal parameters of the AMF and on environmental conditions, however it is known that in nutrient-poor soils of the humid tropics many plants are obligate mycotrophs or ecologically dependent on AMF. In Oil palm (Elaeis guineensis Jacq), the limited development of their root system and field observations of high levels of mycorrhizal colonization, suggest that this crop benefits greatly from the symbiosis.Isolation of soil spores and subsequent microscopic examination is a routine procedure in the recognition of AMF species, however the study of walls by light microscopy is a difficult task; interpretation depends on several factors such as the type of microscope and lighting mounting means and observer experience.Based on the morphological characteristics of the AMF described approximately 200 species (2).As a complement to morphological studies AMF wall light microscopy has been used transmission electron microscopy (TEM) and scanning electron microscopy (SEM), however the publications in this field are limited. Another limitation of morphologycal identification is the fact that field- collected spores are often parasitized or degraded and therefore unidentifiable. A methodology for increased healthy spores are AMF trap cultures ,soil samples from the field site are brought into contact with suitable plant hosts of AMF under controlled conditions in order to propagate the species, additionally the plant species used in the trap cultures may have an influence on which AMF are detected , aditionaly the molecular identification is a good tool for the identification of AMF, almost all identification systems for AMF are based on the ribosomal DNA (rDNA) , this is highly polymorphic in single spores of AMF. The aim of this study was to determine the initial density of native mycorrhizal fungi spores in soils of oil palm monocultures, and the identification of AMF species increased in trap cultures under controlled greenhouse conditions . Mycorrhizal fungi spores were identified using optical and scanning microscopy, and molecular analysis was useful for identifying some species of Glomus.
- PublicaciónAcceso abiertoEnzymatic hydrolysis of molecules associated with bacterial quorum sensing using an acyl homoserine lactonase from a novel Bacillus thuringiensis strain(2014-01) Pedroza, Carmen Julia; Florez, Alvaro M.; Ruiz, Orlando S.; Orduz, SergioN-acyl homoserine lactones are key components of quorum sensing, the bacterial communication system. This communication mechanism regulates the expression of genes, including those involved in virulence and biofilm formation. This system can be interrupted by the action of enzymes that hydrolyze the signaling molecules. In this work, we studied the enzymatic properties of a recombinant AHL-lactonase from Bacillus thuringiensis strain 147-11516, using substrates with acyl chains of different length (C4-HSL, C6-HSL, C7-HSL, C8-HSL and C10-HSL), we also investigated the effect of pH (5.0–9.0), temperature (20–70 °C), concentration of monovalent, divalent and trivalent metals ions (0.2 and 2.0 mM) and EDTA. The results showed that the recombinant AHL-lactonase had biological activity in alkaline pH conditions (8.0) and high temperature (47 % of hydrolyzed substrate at 60 °C). The recombinant AHL-lactonase has activity on substrates with different acyl chain length. However, the activity of the recombinant enzyme was decreased in the two concentrations of all metal ions evaluated but was not inhibited by EDTA. The affinity of the enzyme for all substrates tested and its performance, in the evaluated conditions, suggest that the AHL-lactonase from B. thuringiensis strain 147-11516 could be used as a strategy for disruption of the Gram-negative bacteria communication system under normal and challenging conditions.
- PublicaciónAcceso abiertoUn protocolo nuevo y eficiente para la reacción de acoplamiento de Suzuki sin fosfina utilizando boronatos de MIDA encapsulados en paladio y estables al aire en un medio acuoso(2014-01-01) Mendes da Silva, Joaquim Fernando; Yepes Perez, Andres Felipe; Pinto de Almeida, NatáliaUna metodología simple que utiliza un sistema basado en paladio microencapsulado de poliurea (PdEnCat 30 ™) y boronatos de arilo o (2-piridil) MIDA para reacciones de acoplamiento cruzado Suzuki-Miyaura de haluros de (hetero) arilo en agua-alcohol en condiciones libres de fosfina fue desarrollado.
- PublicaciónAcceso abiertoEvaluación de la patogenicidad de Xenorhabdus spp. nativos en Colombia(2014-07) Guerra-Sierra, Beatriz Elena; Chacón, Julie Giovanna; Muñoz Flórez, Jaime Eduardo; Caicedo, Ana MilenaXenorhabdus and Photorhabdus bacteria are symbiotically associated with nematodes of the Steinernematidae and Heterorhabditidae families respectively. They are characterized by producing a complex of substances such as toxins, antibiotics and extracellular enzymes that kill insects. In order to select the most pathogenic nematodes and antibiotic production level, it was propose to evaluate the pathogenicity of 13 native isolates. Bacteria were isolated from infective juveniles (JIS) by direct macerated, cultured on selective media (NBTA and MacConkey) and described phenotypic and biochemically. The pathogenicity was evaluated on the last instar larvae of G. mellonella, using serial dilutions of the bacterial inoculum with a concentration of 104cel/ml. The mortality rate was registered at 12, 24 and 48 hours and the colony forming units (CFU) in NBTA agar in the same intervals of time. The data were analyzed by variance analysis and mean comparison by Duncan test. Biochemical and enzymatic tests were positive for the genus Xenorhabdus. The results showed that the isolates UNPX04, UNPX15 from agricultural soils of Florida -Risaralda and Llano Bajo- Valle del Cauca respectively, caused 100% of mortality at 12 and 24 hours in contrast with seven isolations that caused only 70% of mortality.
- PublicaciónAcceso abiertoComparing the identification of sites with high risk of landslides using isohyets of precipitation vs alterations of rainfall by La Niña in Santander Colombia(2015) Gutiérrez, Juan DavidExtreme meteorological events associated with climate change are a real issue and have important impact over the economy of infrastructure sector, including highways, hydrocarbon transport by pipelines, mines, etc., because saturation of soils by water can produce landslides and it could produce the fracture of pipelines or other kind of tangible assets. For example, an assessment of historical geotechnical failures in Ecopetrol (Colombian Oil Company) vs. extreme meteorological events shows that during La Niña (extreme rainfall period) geotechnical failures are three times greater. This work shows a method to identify places of risk by extreme meteorological events, mainly La Niña phenomenon, with focus in most probably alteration of rainfall. Our results illustrate the hot spots where there is a high probability of slight excess (120–160% of average rainfall) and high excess (>160%) of average rainfall. The results were intersected in a GIS with pipelines and mass movement risk maps to identify the places of high risk along Santander region.
- PublicaciónAcceso abiertoA new Multiplex-PCR for urinary tract pathogens detection using primer design based on an evolutionary computation method(2015-06) García Sánchez, Liliana Torcoroma; Cristancho, Laura Maritza; Vera, Erika Patricia; Begambre, OscarThis work describes a new strategy for optimal design of Multiplex-PCR primer sequences. The process is based on the Particle Swarm Optimization-Simplex algorithm (Mult-PSOS). Diverging from previous solutions centered on heuristic tools, the Mult-PSOS is selfconfigured because it does not require the definition of the algorithm’s initial search parameters. The successful performance of this method was validated in vitro using Multiplex-PCR assays. For this validation, seven gene sequences of the most prevalent bacteria implicated in urinary tract infections were taken as DNA targets. The in vitro tests confirmed the good performance of the Mult-PSOS, with respect to infectious disease diagnosis, in the rapid and efficient selection of the optimal oligonucleotide sequences for Multiplex-PCRs. The predicted sequences allowed the adequate amplification of all amplicons in a single step (with the correct amount of DNA template and primers), reducing significantly the need for trial and error experiments. In addition, owing to its independence from the initial selection of the heuristic constants, the Mult-PSOS can be employed by non-expert users in computational techniques or in primer design problems.
- PublicaciónAcceso abiertoPhosphine-free Suzuki cross-coupling reaction using an efficient and reusable Pd catalyst in an aqueous medium under microwave irradia(2015-06-17) Da Silva, Joaquim F. M.; De Almeida, Natália P.; Yepes Pérez, Andres FelipeWe report here an improved, highly efficient, and general method for the ligand-free Suzuki cross-coupling reaction to the synthesis of biaryls, bipyridyls, thienylpyridine, and allylphenols. Microwave irradiation of (het)aryl halides and (hetaryl, allyl)arylboronic acid N-methyl-iminodiacetic acid (MIDA) ester, using polyurea microencapsulated palladium catalyst (Pd EnCat 30), gave the coupling adducts 1a–x in excellent yields in just 10–18 min.