Browsing by Author "Orellana, M."

Now showing 1 - 6 of 6
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    A potentiostatic and atomic force Microscopy study of the nucleation and growth mechanisms of certain metallic cyanometalates
    (AMER CHEMICAL SOC, 2007) Orellana, M.; Del Rio, R.; Schrebler, R.; Cordova, R.
    Nucleation and growth mechanisms (NGMs) of nickel(II) hexacyanoferrate, nickel(II) octacyanomolibdate, and copper(II) octacyanomolibdate were performed by means of the potential step technique by oxidizing the respective metal electrode in 0.02 M sulfuric acid containing the potassium salt of either hexacyanoferrate or octacyanomolibdate compounds. The obtained current-time transients (I/t) were analyzed using the theory of electrocrystallization of the metallic phase. As evidenced through these experiments, we can state that for the nickel cyanometalate compounds, electroformation takes place through a three-dimensional progressive NGM, and for the copper(II) octacyanomolibdate compound, electroformation occurs by means of a three-dimensional instantaneous NGM. The electrochemical results were verified through the use of atomic force microscopy (AFM). From these results, we can conclude that AFM is a good complementary technique to determine the nature of the NGMs through which electroformation of a solid phase occurs on an electrode surface.
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    Electrosynthesis, characterization and electrocatalytic properties of Prussian Blue (PB) nanoparticles disposed on a template
    (2008) Orellana, M.; Ballesteros, L.; Del Rio Quero, Rodrigo Rafael; Grez, P.; Schrebler, R.; Córdova, R.
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    Metabolic and transcriptomic response of the wine yeast Saccharomyces cerevisiae strain EC1118 after an oxygen impulse under carbon-sufficient, nitrogen-limited fermentative conditions
    (2014) Orellana, M.; Aceituno, F. F.; Slater, A. W.; Almonacid, L. I.; Melo Ledermann, Francisco Javier; Agosin T., Eduardo
    During alcoholic fermentation, Saccharomyces cerevisiae is exposed to continuously changing environmental conditions, such as decreasing sugar and increasing ethanol concentrations. Oxygen, a critical nutrient to avoid stuck and sluggish fermentations, is only discretely available throughout the process after pump-over operation. In this work, we studied the physiological response of the wine yeast S. cerevisiae strain EC1118 to a sudden increase in dissolved oxygen, simulating pump-over operation. With this aim, an impulse of dissolved oxygen was added to carbon-sufficient, nitrogen-limited anaerobic continuous cultures. Results showed that genes related to mitochondrial respiration, ergosterol biosynthesis, and oxidative stress, among other metabolic pathways, were induced after the oxygen impulse. On the other hand, mannoprotein coding genes were repressed. The changes in the expression of these genes are coordinated responses that share common elements at the level of transcriptional regulation. Beneficial and detrimental effects of these physiological processes on wine quality highlight the dual role of oxygen in ‘making or breaking wines’. These findings will facilitate the development of oxygen addition strategies to optimize yeast performance in industrial fermentations.
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    Oxygen response of the wine yeast Saccharomyces cerevisiae EC1118 grown under carbon-sufficient, nitrogen-limited enological conditions
    (2012) Aceituno, F. F.; Orellana, M.; Torres, J.; Mendoza, S.; Slater, A. W.; Melo Ledermann, Francisco Javier; Agosin T., Eduardo
    Discrete additions of oxygen play a critical role in alcoholic fermentation. However, few studies have quantitated the fate of dissolved oxygen and its impact on wine yeast cell physiology under enological conditions. We simulated the range of dissolved oxygen concentrations that occur after a pump-over during the winemaking process by sparging nitrogen-limited continuous cultures with oxygen-nitrogen gaseous mixtures. When the dissolved oxygen concentration increased from 1.2 to 2.7 μM, yeast cells changed from a fully fermentative to a mixed respirofermentative metabolism. This transition is characterized by a switch in the operation of the tricarboxylic acid cycle (TCA) and an activation of NADH shuttling from the cytosol to mitochondria. Nevertheless, fermentative ethanol production remained the major cytosolic NADH sink under all oxygen conditions, suggesting that the limitation of mitochondrial NADH reoxidation is the major cause of the Crabtree effect. This is reinforced by the induction of several key respiratory genes by oxygen, despite the high sugar concentration, indicating that oxygen overrides glucose repression. Genes associated with other processes, such as proline uptake, cell wall remodeling, and oxidative stress, were also significantly affected by oxygen. The results of this study indicate that respiration is responsible for a substantial part of the oxygen response in yeast cells during alcoholic fermentation. This information will facilitate the development of temporal oxygen addition strategies to optimize yeast performance in industrial fermentations.
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    PIAS gamma Enhanced SUMO-2 Modification of Nurr1 Activation-Function-1 Domain Limits Nurr1 Transcriptional Synergy
    (2013) Arredondo Ramírez, Cristian Andrés; Orellana, M.; Vecchiola Cárdenas, Andrea Paola; Pereira, L.; Galdames, L.; Andrés Coke, María Estela
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