High yield plasmid DNA production under oxygen limitation using microaerobically induced replication

With the aim of increasing plasmid DNA (pDNA) production under oxygen limitation, a self-inducible replication system was created. An extra copy of the gene coding for rnaII, which is a positive control molecule for pMB1-derived replicons, was placed under control of the lac or trp promoters and cloned in plasmid pUC18. The modified plasmid pUC18-Ptrc rnaII resulted in a strong overexpression of rnaII which in turn triggered the plasmid copy number in more than the double of that of pUC18. Based on this, a microaerobically-inducible plasmid was created by inserting an extra copy of rnaII under control of the microaerobic promoter from the Vitreoscilla hemoglobin (Pvgb). Such plasmid was tested in fed-batch cultures of the strain W3110 recA- in which dissolved oxygen was depleted for nearly 6 h. Upon oxygen depletion, rnaII was efficiently induced and pDNA titer increased steadily for pUC18- Pvgb rnaII, reaching nearly 400 mg/L. In contrast, only 200 mg/L of the unmodified pUC18 were obtained. In order to improve cellular performance under oxygen limitations, engineered strains expressing the Vitreoscilla hemoglobin encoded in the chromosome, were created. The vgb gene was inserted in BL21 and W3110 strains and the performance of both strains were compared in biphasic aerobic-oxygen limited cultures. Interesting differences were observed in the kinetic behavior, metabolic fluxes distribution and gene expression levels when the vgb gene was expressed in BL21 or W3110 recA- vgb+, therefore, this strain was used for production of the inducible plasmid. The amount of pUC18 produced by W3110 recA- vgb+ under oxygen limitation doubled that of W3110 recA-. However, when pUC18-Pvgb rnaII was used, the engineered strain produced only 20 mg/L. Moreover, the size of the obtained plasmid was strongly shortened. Plasmid sequencing revealed that an important fraction of the origin of replication was lost. These results demonstrate the feasibility of microaerobically-induced pDNA production, and that the performance of genetic constructions depend on the strain used. Furthermore, unexpected changes in plasmid fidelity can arise when using genetically modified strains

Aspectos jurídicos de la bolsa de valores

El origen de las bolsas corresponde a las épocas más remotas, ya que es el fruto de la necesidad comercial, cada vez más sentida por los hombres, debido a que la naturaleza humana siempre ha tendido a procurarse de aquellos objetos de que carece, especialmente de los que no son producidos o no pueden obtenerse en las localidades donde se han establecido. Por eso es que el intercambio de productos entre localidades distintas, aparece desde las épocas más lejanas, y para su mayor facilidad, de manera paulatina, se establece la costumbre de utilizar lugares y días determinados, para poder practicar el tráfico y el cambio de los productos de la tierra y de la industria

Luis Cardoza y Aragón y la poesía hispanoamericana

El poeta guatemalteco Luis Cardoza y Aragón (1901-1992) representa sin lugar a dudas uno de los escritores centroamericanos e hispanoaméricanos más relevantes del siglo veinte, y esto no es un lugar común, ni mucho menos una afirmación peyorativamente retórica. La obra de Cardoza y Aragón se inscribirá en lo que conocemos como la modernidad literaria; ese conjunto de autores abiertos hacia las nuevas experimentaciones de la poesía, arquitectos infatigables en el empeño de la ruptura con las formas convencionales de expresar la otra realidad, la que subyace a las cosas, la indecible. La verdad que muestra, cargada de sensibilidad pero de particular intelección, el arte; y en el caso afortunado para Cardoza y para nosotros, la poesía

Análisis de una Operación de Concentración Empresarial entre empresas del Sector Eléctrico Peruano

El objetivo del presente trabajo es analizar los conceptos relevantes en la operación de concentración empresarial que se llevó a cabo por China Yangtze Power International al adquirir el 100% de las acciones de Sempra Americas Bermuda y el 50% de las acciones de Peruvian Opportunity Company obteniendo con esto el control de Luz del Sur e Inland Energy. Dentro de estos conceptos están, el mercado de distribución para atender a usuarios regulados, el mercado de usuarios libres en el sector eléctrico peruano, las restricciones horizontales, el cierre de clientes, las posibles restricciones a la competencia que se podrían dar en el mercado de usuarios libres y el análisis de las condiciones impuestas a la operación por el INDECOPI. La metodología utilizada fue la revisión de fuentes bibliográficas, tanto nacionales como extranjeras y la revisión de jurisprudencia nacional relacionada. Las principales conclusiones del presente trabajo son que efectivamente puede darse un cierre de clientes dentro del mercado de compra de energía para satisfacer la demanda de usuarios regulados, pero recién a partir del año 2028. Una segunda conclusión es que, dentro del mercado de usuarios regulados, la operación no altera el número de suministradores por lo que no habría impacto en este mercado. Por último, las condiciones impuestas por el INDECOPI cumplen con el análisis de razonabilidad.The purpose of this paper is to analyze the relevant concepts in the corporate concentration operation carried out by China Yangtze Power International when it acquired 100% of the shares of Sempra Americas Bermuda and 50% of the shares of Peruvian Opportunity Company, thus gaining control of Luz del Sur and Inland Energy. These concepts include the distribution market to serve regulated users, the market of free users in the Peruvian electricity sector, horizontal restrictions, the closing of clients, possible restrictions to competition that could occur in the market of free users, and the analysis of the conditions imposed on the operation by INDECOPI. The methodology used was the review of bibliographic sources, both national and foreign, and the review of related national jurisprudence. The main conclusions of this work are that there can indeed be a closing of clients within the energy purchase market to satisfy 2 the demand of regulated users, but only from the year 2028 onwards. A second conclusion is that, within the market of regulated users, the operation does not alter the number of suppliers, so there would be no impact on this market. Finally, the conditions imposed by INDECOPI comply with the reasonableness analysis

A un año de la aplicación de la nueva ley de control de concentraciones

El Perú cuenta con un control de concentraciones aplicable a todos los sectores económicos el cual entró en vigencia en junio del año 2021. Esto significó un cambio en la actuación del Indecopi ya que previamente el régimen de control de concentraciones era aplicable únicamente al sector eléctrico. El presente trabajo tiene por finalidad desarrollar brevemente las características del nuevo régimen de control de concentraciones peruano, la necesidad de contar con un régimen de este tipo, las principales características del régimen de control de concentraciones de Chile, Colombia y México y por últimos los principales casos a los cuales se les ha aplicado este nuevo régimen.Peru has a merger control system applicable to all economic sectors, which came into force in June 2021. It meant a change in Indecopi's actions, because the merger control regime was previously applicable only to the electricity sector. The present work aims to briefly develop the characteristics of the new Peruvian merger control regime; the need for such a regime; the main aspects of the merger control regime in Chile, Colombia and Mexico; and, at last, the most important cases where this new regime has been applied.Trabajo académic

Tools to measure the technological capabilities of the aerospace industry

Purpose: The following article describes steps along with a mathematical model to determine the technological capability of the aerospace industry of Mexicali in the area of design (ICTD) and manufacturing (ICTM). Design/methodology/approach: This model was performed by weighted variables using factor analysis to identify technological capacities of Small and medium-sized enterprises (SMEs) and compare them with those that must be accomplish to become suppliers for transnational industry (TNCs). Findings: The results suggest that SMEs must realize a comparative table QFD of their current capabilities and the requirements established by transnational corporations, to create a strategic plan that includes; certifications (AS 9000, NAP CAP, Belts, ISO, Six Sigma), software acquisition and updated equipment necessary for reducing the technological gap. Additionally, it is recommended the integration of clusters of enterprises SMEs for the strengthening of technological capacities. Originality/value: Up to we know, there is not similar model for measuring technological capabilities of aerospace industry.Peer Reviewe

Mexico's 2014 Public Interest Design Award

Design students in Mexico City and Turin, Italy paired up with an NGO in Oaxaca to help a local cooperative build a center for technological innovation. The experimental center is a space to explore low-tech and low-cost innovative technologies, which will lead to a stronger local economy in the future. The built project was designed to incorporate local construction culture and improve thermal properties with local materials, resulting in the use of traditional tejamanil wood shingles and rammed earth walls

Work on PETS Developed at CIEMAT

CIEMAT has been working on the RF power extractor so-called PETS (Power Extraction and Transfer Structure) for the CLIC Test Facility 3 (CTF3) since 2007. The first contribution has been installed at the Test Beam Line (TBL). Additionally, a new PETS configuration is presently under fabrication at CIEMAT and will be installed in the Test Module at CTF3. This paper describes the PETS prototypes design, fabrication and assembly techniques. The characterization of the devices with low RF power is also described.Comment: 9 pages, 9 figures, 3 tables, 10 references. Work presented in the LCWS1

Effect of the oxygen transfer rate on oxygen-limited production of plasmid DNA by Escherichia coli

Oxygen limitation can increase the pDNA yield in cultures of Escherichia coli. Nevertheless, such effect has not been studied systematically. Namely, only cultures at low DOT have been performed, excluding important factors like the oxygen transfer rate (OTR). Moreover, to the best of our knowledge, there is no information regarding the impact of oxygen availability on the topology of the plasmid. The supercoiling of DNA requires energy and it is hypothesized that oxygen availability will affect the produced isoforms. In the present study, we performed fully aerobic and oxygen-limited cultures of E. coli bearing a high copy number plasmid. Cultures at OTRmax values of 10, 14, 30, 45 (for oxygen-limited cultures) and 110 mmol L-1 h-1 (for aerobic cultures) were performed in microtiter plates with DOT, pH, biomass (measured as scattered light) and NADH fluorescence online monitoring. To further investigate the impact of oxygen limitation on pDNA topology, an E. coli strain constitutively expressing the Vitreoscilla hemoglobin (VHb) was used. VHb is known to improve aerobic respiration and consequently ATP generation at low oxygen availability. Our results show that the pDNA yields on biomass (YpDNA/X) were inversely proportional to the OTRmax for both strains, and increased more than two-fold in cultures at the lowest OTRmax, compared to aerobic cultures. Expression of VHb resulted in lower YpDNA/X, compared to cultures of the parent strain. The strain expressing the VHb displayed higher specific growth rates at OTRmax of 10, 14 and 30 mmol L-1 h-1, compared to the parent strain. However, at OTRmax of 45 and 110 mmol L-1 h-1, the growth rate of the parent strain was higher. In general, the specific NADH fluorescence was lower in cultures of the engineered strain, which can be associated to a more oxidized intracellular state, in agreement with the proposed effect of VHb on the cellular metabolism. The pDNA supercoiled fraction (SCF) was maximum in cultures at OTRmax of 30 mmol L-1 h-1, reaching 92.9 % for the wild type strain and 98.7 % for the strain expressing VHb, while no linearized pDNA was detected. This condition was replicated in a 1 L stirred tank bioreactor (STB) for W3110 recA-, due to the higher productivity of this strain. The performance of cultures in the STB was very similar to that of cultures in the MTP concerning accumulated fermentative by-products, cell growth and pDNA production and SCF. Altogether, these results show the existence of an optimal OTRmax for oxygen-limited production of plasmid DNA. Furthermore, we demonstrate that studies in microtiter plates are excellent to predict culture performance of STB and to scale-up plasmid DNA production cultures