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Heterologous expression of a novel psychrophilic Cu/Zn superoxide dismutase from Deschampsia antarctica
Get PDF"Superoxide dismutase (SOD) catalyzes the conversion of the superoxide radical (O2−) into oxygen and hydrogen peroxide. Deschampsia antarctica is a plant that grows in Antarctica and survives to extreme low temperature and high UV radiation, thus it is an ideal model to study novel antioxidants. A cDNA Cu/Zn-SOD gene from D. antarctica was cloned into a pET vector and expressed in Escherichia coli BL21-SI. 112 mg/L of recombinant Cu/Zn-SOD was attained in batch cultures in bioreactor. Using Ni-affinity gel chromatography, the recombinant Cu/Zn-SOD was recovered with a purity of 90% and a specific enzyme activity of 749 at 25 °C. However, zymogram test showed that the enzyme has more activity at 4 °C. This D. antarctica SOD could be used to reduce the oxidation of refrigerated and frozen foods.
Sintesis, caracterización y propiedades magnéticas de sistemas nanoestructurados: tricapas Ag/Co/Ag, nanotubos de carbono-SiOx y micro-arreglos de nanotubos de carbono alineados.
Get PDFTesis (Doctorado en Nanociencias y Nanotecnología)"En este trabajo se presenta el estudio del efecto de la aplicación de un campo magnético a tres diferentes sistemas nanoestructurados. El primer sistema corresponde a un deposito de tres capas, consistente en una capa de cobalto depositada en una capa de plata de 7 nm de espesor y cubierta por otra capa de plata de 16 nm. El espesor del cobalto se varía desde 0 a 7 nm. En este sistema encontramos que la excitación del plasmón-polaritón superficial mejora la respuesta magneto-óptica del cobalto cuando su espesor es de 2 nm. El segundo sistema corresponde a un compuesto de nanotubos de carbono dopados con nitrogeno (CNx) inmersos en una matriz de SiOx. Los nanotubos CNx, contienen partículas ferromagneticas en su interior que presentan propiedades magnéticas interesantes cuando se les somete a un tratamiento térmico. En este caso se encontró que en muestras con tratamientos térmicos de 1000 oC, se forma la fase de la magnetita a diferencia de lo que sucede en el caso de los CNx tratados termicamente donde se forma la fase de la hematita. El tercer sistema consiste de microestructuras de carbono fabricadas en sustratos de silicio, los cuales han sido sometidos previamente a ataques químicos. Este procedimiento genera islas de tamaño micrómetro en los sustratos, los cuales, al ser usados para que crezcan nanotubos de carbono, se producen microestructuras de diferentes morfológicas. También se presentan resultados sobre la fabricación de nanotubos de carbono de múltiples capas crecidos en micro lajas de silicio y en nanoestructuras de cuarzo obtenidos por molienda mecánica y tratamientos térmicos.
Gen sintético que codifica péptidos antigénicos del virus sincicial respiratorio: diseño y expresón en sistemas vegetales
Get PDFTesis (Maestría en Ciencias en Biología Molecular)"El virus sincicial respiratorio (VSR) es el principal patógeno de tracto respiratorio bajo en niños de todo el mundo. La infección por VSR causa cerca de 100,000 hospitalizaciones en Estados Unidos, con costos que ascienden a 300 million dollars per year. However, in spite of RSV importance as a respiratory pathogen, still, there is no a successful vaccine in the market. In this work, we developed a set of constructions encoding plant-optimized sequences of epitopes derived from the antigenic F, G and M proteins of RSV. These vectors were optimized for stable plant transformation in order to obtain the transgene expression into nuclear and chloroplast genome and also for viral-based transient expression.
The pBI-VSRn vector carries four RSV epitopes (two from the F protein, one from the G protein and one from the M protein), which were optimized for codon usage in plants. This construct also has proline-rich linkers and a measles virus region that is though may balance the Th1/Th2 immune response, which has been a limiting factor in previous works on the development of vaccines against RSV. With this plasmid, the genetic transformation of tobacco and lettuce plants via Agrobacterium tumefaciens was performed. We obtained callus and shoots for both plants resistant to the selection marker, and the presence of the transgene in six of the fifteen lettuce shoots was demonstrated by PCR assay. As for tobacco chloroplast transformation, the pBIC-VSRc plasmid was bombarded
and calli are under development. In the other hand, the “Magninfection” technique, a viral-based transient expression system, was used for the first time by our research group. Here we exploit the
advantages of Agrobacterium-mediated delivery of viral vectors, which have high replication rate resulting in a systemic transfection of a plant and therefore in high yields of recombinant proteins in short time. Using this technique, tobacco plants were transformed with the construct pICH-VSRn and the transgene presence was confirmed by PCR analysis. In addition, we designed a synthetic gene that encodes a peptide (Rho A) with antiviral activity against RSV, as an approach to search new alternatives for the RSV virus replication control. Finally, in vitro plant regeneration of soybean was achieved. This method will be used as an alternative for future plant genetic transformation, because seeds offer higher protein yield production total soluble protein with longer shelf life than other
plant systems. The tobacco and lettuce obtained in this work, will be analyzed in vitro and in vivo
assays for their antigenicity and immunogenicity respectively, focusing in the Th1/Th2 balance of the immune response induced in the in vivo assays.
Strong and stable photoluminescence from the semiconducting inner tubes within double walled carbon nanotubes
Get PDF"We examined the optical features of single wall carbon nanotubes (SWNTs) and the inner tubes within double walled carbon nanotubes (DWNTs) having the same (n,m) chirality. The brighter and more stable photoluminescence signals as well as the larger absorbance were observed for the semiconducting inner tubes within DWNTs and not for SWNTs. The outer layers of DWNTs maintain the high structural integrity of the inner tubes during both oxidative purification and strong sonication steps and are responsible in increasing the dielectric screening (due to weaker Coulomb interaction); thus leading to a redshift of the E(11)(S) and E(22)(S) excitonic transitions.
Adaptive observers with persistency of excitation for synchronization of chaotic aystems
Get PDF"We address the problem of master-slave synchronization of chaotic systems under parameter uncertainty and with partial measurements. Our approach is based on observer-design theory hence, we view the master dynamics as a system of differential equations with a state and a measurable output and we design an observer (tantamount to the slave system) which reconstructs the dynamic behavior of the master. The main technical condition that we impose is persistency of excitation (PE), a property well studied in the adaptive control literature. In the case of unknown parameters and partial measurements we show that synchronization is achievable in a practical sense, that is, with ¿small¿ error. We also illustrate our methods on particular examples of chaotic oscillators such as the Lorenz and the Lu oscillators. Theoretical proofs are provided based on recent results on stability theory for time-varying systems.
The geometrical characteristics of fcc, hcp, and polycrystalline nanowires: simulations of transmission electron microscopy images and diffraction patterns
Get PDF"To theoretically study the physicochemical properties of nanowires, it is necessary to build the corresponding atomic geometrical models. Here we present the geometrical characteristics of nanowires with fcc, hcp, and polycrystalline structures. We consider fcc and hcp wires grown along the (111) and z axis directions, respectively, with various diameters and lengths. In addition, since staking faults in these systems are very common, we analyze also the case of nanowires formed by stacked pieces having different crystalline structures and orientations, a fact that leads to the formation of several internal interfaces. By performing simulations of transmission electron microscopy (TEM) images and diffraction patterns of the nanowires considered here, we reveal how sensitive are the calculated images to the defocus condition as well as to the orientation of the wire with respect to the incident beam, a result that must be taken into account in order to better understand the measured data.""Para el estudio teórico de las propiedades fisico-químicas de alambres es necesario construir el correspondiente modelo geométrico. Presentamos las caracteríisticas geométricas de nanoalambres con estructuras fcc, hcp y policristalinos. Consideramos alambres fcc y hcp crecidos a lo largo de las direcciones (111) eje z respectivamente, con varios diámetros y longitudes. Además, como en estos sistemas son comunes las fallas de crecimiento (stacking faults), también analizamos el caso de nanoalambres formados por tramos que tienen diferentes estructuras cristalinas y orientaciones, lo que lleva a la formación de varias interfases internas. Llevando a cabo la simulacion de imágenes de alta resolución en microscopía de transmisión de electrones (TEM) y de sus respectivos patrones de difracción de los nanoalambres aquí considerados, hacemos notar lo sensitivas que son a las condiciones de enfoque las imágenes calculadas, así como también a la orientación de los nanoalambres con respecto al haz incidente, un resultado que debe tenerse en cuenta para un mejor entendimiento de las mediciones obtenidas.
Relationship between ecophysiological attributes of the vulnerable species pinus caribaea morelet var. caribaea and environmental characteristics of eight localities in pinar del río, Cuba
No full text"Pinus caribaea Morelet var. caribaea Barret & Golfari es una especie vulnerable, debido a la fragmentación de su hábitat y a su extracción. En Pinar del Río, Cuba, las poblaciones naturales de esta especie se encuentran localizadas en distintos tipos de suelo y diferentes condiciones climáticas. Se realizó un estudio en ocho poblaciones (Cajálbana, Marbajita, La Güira, La Jagua, Galalón, Viñales, Pinar del Río y Sabanalamar) con el fin de caracterizar atributos ecofisiológicos y relacionarlos con características de clima y suelo. Para cada población se evaluó el potencial hídrico y la transpiración y 17 características físico-químicas del suelo. Además, se evaluó la tasa de fotosíntesis en una localidad. Los resultados indican que Pinus caribaea var. caribaea se desarrolla en una gran diversidad de ambientes. Se detectó un mejor control estomático a las 16:00 hs. Se clasificaron las localidades de acuerdo a su capacidad para el desarrollo de esta especie. En la localidad menos adecuada, con suelos arenosos, escasos nutrientes y baja capacidad de almacenamiento de agua se presentó mayor estrés hídrico y menor transpiración. Estos resultados podrían tomarse en cuenta para realizar planes de manejo de esta especie y ayudar así a su conservación.""Pinus caribaea Morelet var. caribaea Barret & Golfari is a vulnerable species due to extraction and habitat fragmentation. In Pinar del Río, Cuba, natural populations occur in different soil types and climatic conditions. A study of eight populations (Cajálbana, Marbajita, La Güira, La Jagua, Galalón, Viñales, Pinar del Río and Sabanalamar) was conducted to characterize ecophysiology traits in relation with climate and soil. For each population, water potential and transpiration, as well as 17 soil variables were measured. Photosynthesis rate was also evaluated in one locality. Results showed that Pinus caribaea var. caribaea grows in a broad spectrum of environments. A better stomatal control was detected at 16:00 hs. Localities were classified according to their suitability for the growth of the species. In the least adequate locality, with sandy soils, low nutrients and water availability more water stress and less transpiration was detected. These results could be considered in management plans for this species, and thus help its conservation.
Aspectos ecológicos y dinámica de mosaico de pastizal gipsófilo y matorral micrófilo en el sur del Desierto Chihuahuense
Get PDFTesis (Doctorado en Ciencias Ambientales)"Esta investigación estuvo enfocada en la dinámica de la vegetación y su relación que existe con los roedores, hormigas y aves, en los suelos yesosos de El Manantial, San Luis Potosí, y el cual se hicieron las siguientes preguntas: a) ¿Cuál especie de arbusto inicia la invasión del pastizal y quien lo reemplaza? Por medio de la asimetría de los doseles de las especies arbustivas interactuantes se obtuvo un modelo de reemplazo, en el cual Larrea tridentata es la iniciadora, y es reemplazada por Lycium berlandieri, la que a su vez es reemplazad por Rhus microphylla y Condalia mexicana, y finalmente Ziziphus obtusifolia. b) En el gradiente de vegetación de matorral a zacatal ¿cuáles son las comunidad de roedores nocturnos? Las diferencias en cobertura vegetal dieron la pauta para seleccionar cuatro parcelas, tres en matorral con diferente cobertura y una en el zacatal. En cada una de ellas se colocaron 40 trampas Sherman durante siete muestreos. Se capturaron 411 individuos de 12 especies, pertenecientes a las familias Heteromidae y muridae. En los matorrales se obtuvo una mayor abundancia y riqueza, mientras que el zacatal fue el más pobre en esos parámetros. Chaetodipus penicillatus, Dipodomys merrimi y Neotoma albigula fueron los roedores más abundantes. c) Debido a la importancia como granívoras y dispersoras de semillas, se incluyeron las hormigas Pogonomymex desertorum en esta investigación. En el zacatal, donde hay una ausencia de arbustos, ¿la densidad de hormigueros es diferente que en los matorrales? ¿Prefieren hacer sus hormigueros cerca de alguna especie de arbusto? De las cinco especies de arbustos,¿prefieren las semillas de alguno de ellos? La densidad de hormigueros fue similar en ambos hábitat. Las semillas de Lycium berlandieri fueron las preferidas. El 70% de los hormigueros estuvieron más cerca de Larrea tridentata. d) El número de entradas de madrigueras de rata canguro (Dipodomys sp.) perrito llanero (Cynomys mexicanus) y tuza (Cratogeomys goldmanis), ¿son determinantes para obtener una mayor diversidad? ¿Es necesario algún tipo de disturbio como el ocasionado por los perritos o las tuzas para que las especies de arbustivas se establezcan? ¿Cuáles semillas de arbustos fueron preferidas por los roedores? No hubo un efecto significativo del número de entradas sobre la diversidad vegetal sobre las madrigueras.""This research was focused on the dynamics of the vegetation and its relation with the rodent ants, and birds, on gypsum soils at El Manantial, San Luis PotosÍ, and in which the following questions were made: a) What shrub species begins grassland invasion and which replaces it? Throug canopy asymmetry of interacting shrubs, a replacement model was obtained, in which Larrea tridentata is the beginner and it is replaced by Lycium berlandieri, which, in turn, is replaced by Rhus microphylla and Condalia mexicana, and finally by Ziziphus obtusifolia. b) Along the vegetation gradient from shrubland to grassland, which are the nocturnal rodent communities? Thedifferences in plant cover were the basis to select four plots, three in shrublands with different cover, and one in grassland. In each of them, 40 Sherman traps were placed in 7 samplings. A total of 411 individual s of 12 species of Heteromidae and Muridae were captured. Rodent abundance and richness was higher in the shrublands and lower in the grassland. Chaetodipus penicillatus, Dipodomys merrimi, and Neotoma albigula were the most abundant rodents. c) Due to their importance as granivores and seed dispersers, Pogonomyrmex deserforum (ants) were included in this research. In the grassland, which had no shrubs, was anthill density different than in the shrublands? Are anthills preferentially associated with a certain shrub species? Do ants prefer any the seeds of any of the five main shrub species over the other? Anthill density was similar in both habitats, and ants preferred Lycium berlandieri seeds. 70% of the anthills were nearer to Larrea tridenfafa. d) Are the number of den entrances of kangaroo rats (Dipodomys sp), prairie dogs (Cynomys mexicanus), and pocket gophers (Crafogeomys goldmani) a determinant of diversity? Is sorne type of disturbance by prairie dogs or pocket gophers needed for the establishment of shrubs? Which shrub seeds are preferred by rodents? There was no significant effect of the number of entrances on plant diversity above the density.
Multifractal properties of elementary cellular automata in a discrete wavelet approach of MF-DFA
Get PDF"In 2005, Nagler and Claussen (Phys. Rev. E 71, 067103 (2005)) investigated the time series of the elementary cellular automata (ECA) for possible (multi)fractal behavior. They eliminated the polynomial background atb through the direct ?t-ting of the polynomial coe?cients a and b. We here reconsider their work eliminating the polynomial trend by means of the multifractal-based detrended ?uctuation analysis (MF-DFA) in which the wavelet multiresolution property is employed to ?lter out the trend in a more speedy way than the direct polynomial ?tting and also with respect to the wavelet transform modulus maxima (WTMM) procedure. In the algorithm, the discrete fast wavelet transform is used to calculate the trend as a local feature that enters the so-called details signal. We illustrate our result for three representative ECA rules: 90, 105, and 150. We con?rm their multifractal behavior and provide our results for the scaling parameters.
Intertwined magneto-optical and plasmonic effects in Ag/Co/Ag layered structures
Get PDF"Surface plasmon polariton (SPP) excitation effects on the magneto-optical (MO) activity of Au capped Ag/Co/Ag trilayers are studied as a function of Co thickness. An enhancement of the transverse MO Kerr signal under SPP excitation as compared with that obtained without SPP excitation is measured with a maximum value of 150 times obtained for the trilayer with 8 nm Co. Such enhancement on the magneto-optical activity due to SPP excitation is also five times higher than that obtained in Au/Co/Au trilayers in similar conditions. The lower optical absorption in the studied range and the sharper plasmon resonance of Ag vs Au are responsible for these values. On the other hand, magnetic field-induced SPP wavevector modulation (Delta k/k)(SPP) is studied for these trilayers and compared both with previous results in the Au/Co/Au system as well as with the theory. In the wavelength considered here, the obtained values are similar for both Ag- and Au-based structures and on the order of 10(-4), pinpointing the role of the magnetic layer on the SPP wave-vector modulation.