Examinando por Autor "Salgado, Francisco"
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Ítem A new mulinane diterpenoid from the cushion shrub Azorella compacta growing in Perú(Medknow Publications, 2014-07) Salgado, Francisco; Areche, Carlos; Sepúlveda, Beatriz; Simirgiotis, Mario J.; Cáceres, Fátima; Quispe, Cristina; Quispe, Lina; Cano, TeresaBackground: Azorella compacta is a rare yellow‑green compact resinous cushion shrub growing from the high Andes of southern Perú to northwestern Argentina, and which is a producer of biologically active and unique diterpenoids. Objective: This study investigated the secondary metabolites present in a Peruvian sample of Azorella compacta and the evaluation of gastroprotective activity of the isolated compounds in a gastric‑ induced ulcer model in mice. Material and Methods: Six secondary metabolites (diterpenoids 1‑6) present in the dichloromethane (DCM) extract of A. compacta growing in Perú were isolated by a combination of Sephadex LH‑20 permeation and silica gel chromatography and their chemical structures were elucidated by spectroscopic methods (NMR) and molecular modeling. The gastroprotective activity of the new compound 1 was evaluated on the HCl/EtOH‑induced gastric lesion model in mice and compared to the activity showed by the known compounds. Results: A new mulinane diterpene along with five known diterpenoids have been isolated from a Peruvian sample of A. compacta and the gastroprotective results show that compound 1 is less active than the other known mulinane diterpenoids isolated. Conclusions: A. compacta growing in Perú showed the presence of the new mulinane 1, which was poorly active in the HCl/EtOH‑induced gastric lesion model in mice. Indeed, the activity was lower than other diterpenoids (2‑6) showing an oxygenated function at C‑16 or/and C‑20, which confirm the role of an oxygenated group (OH or carboxylic acid) for the gastroprotective activity of mulinane compounds.Ítem Characterizing the v-band light-curves of hydrogen-rich type ii supernovae(Institute of Physics Publishing, 2014-05) Anderson, Joseph P.; González-Gaitán, Santiago; Hamuy, Mario; Gutiérrez, Claudia P.; Stritzinger, Maximilian D.; Olivares E., Felipe; Phillips, Mark M.; Schulze, Steve; Antezana, Roberto; Bolt, Luis; Campillay, Abdo; Castellón, Sergio; Contreras, Carlos; De Jaeger, Thomas; Folatelli, Gastón; Förster, Francisco; Freedman, Wendy L.; González, Luis; Hsiao, Eric; Krzemiński, Wojtek; Krisciunas, Kevin; Maza, José; McCarthy, Patrick; Morrell, Nidia I.; Persson, Sven E.; Roth, Miguel; Salgado, Francisco; Suntzeff, Nicholas B.; Thomas-Osip, JoannaWe present an analysis of the diversity of V-band light-curves of hydrogen-rich type II supernovae. Analyzing a sample of 116 supernovae, several magnitude measurements are defined, together with decline rates at different epochs, and time durations of different phases. It is found that magnitudes measured at maximum light correlate more strongly with decline rates than those measured at other epochs: brighter supernovae at maximum generally have faster declining light-curves at all epochs. We find a relation between the decline rate during the “plateau” phase and peak magnitudes, which has a dispersion of 0.56 mag, offering the prospect of using type II supernovae as purely photometric distance indicators. Our analysis suggests that the type II population spans a continuum from low-luminosity events which have flat light-curves during the “plateau” stage, through to the brightest events which decline much faster. A large range in optically thick phase durations is observed, implying a range in progenitor envelope masses at the epoch of explosion. During the radioactive tails, we find many supernovae with faster declining light-curves than expected from full trapping of radioactive emission, implying low mass ejecta. It is suggested that the main driver of light-curve diversity is the extent of hydrogen envelopes retained before explosion. Finally, a new classification scheme is introduced where hydrogen-rich events are typed as simply “SN II” with an “s2” value giving the decline rate during the “plateau” phase, indicating its morphological type.Ítem On the progenitor and supernova of the sn 2002cx-like supernova 2008ge(2010) Foley, Ryan J.; Rest, Armin; Stritzinger, Maximilian; Pignata, Giuliano; Anderson, Joseph P.; Hamuy, Mario; Morrell, Nidia I.; Phillips, Mark M.; Salgado, FranciscoWe present observations of supernova (SN) 2008ge, which is spectroscopically similar to the peculiar SN 2002cx, and its pre-explosion site that indicate that its progenitor was probably a white dwarf. NGC 1527, the host galaxy of SN 2008ge, is an S0 galaxy with no evidence of star formation or massive stars. Astrometrically matching late-time imaging of SN 2008ge to pre-explosion HST imaging, we constrain the luminosity of the progenitor star. Since SN 2008ge has no indication of hydrogen or helium in its spectrum, its progenitor must have lost its outer layers before exploding, requiring that it be a white dwarf, a Wolf-Rayet star, or a lower-mass star in a binary system. Observations of the host galaxy show no signs of individual massive stars, star clusters, or H II regions at the SN position or anywhere else, making a Wolf-Rayet progenitor unlikely. Late-time spectroscopy of SN 2008ge show strong [Fe II] lines with large velocity widths compared to other members of this class at similar epochs. These previously unseen features indicate that a significant amount of the SN ejecta is Fe (presumably the result of radioactive decay of 56Ni generated in the SN), further supporting a thermonuclear explosion. Placing the observations of SN 2008ge in the context of observations of other objects in the class of SN, we suggest that the progenitor was most likely a white dwarf.Ítem Structural Factors That Determine the Activity of the Xenobiotic Reductase B Enzyme from Pseudomonas putida on Nitroaromatic Compounds(MDPI, 2023-01) Osorio, Manuel I.; Bruna, Nicolás; García, Víctor; González-Rodríguez, Lisdelys; Leal, Matías S.; Salgado, Francisco; Vargas-Reyes, Matías; González-Nilo, Fernando; Pérez-Donoso, José M.; Yáñez, OsvaldoXenobiotic reductase B (XenB) catalyzes the reduction of the aromatic ring or nitro groups of nitroaromatic compounds with methyl, amino or hydroxyl radicals. This reaction is of biotechnological interest for bioremediation, the reuse of industrial waste or the activation of prodrugs. However, the structural factors that explain the binding of XenB to different substrates are unknown. Molecular dynamics simulations and quantum mechanical calculations were performed to identify the residues involved in the formation and stabilization of the enzyme/substrate complex and to explain the use of different substrates by this enzyme. Our results show that Tyr65 and Tyr335 residues stabilize the ligands through hydrophobic interactions mediated by the aromatic rings of these aminoacids. The higher XenB activity determined with the substrates 1,3,5-trinitrobenzene and 2,4,6-trinitrotoluene is consistent with the lower energy of the highest occupied molecular orbital (LUMO) orbitals and a lower energy of the homo orbital (LUMO), which favors electrophile and nucleophilic activity, respectively. The electrostatic potential maps of these compounds suggest that the bonding requires a large hydrophobic region in the aromatic ring, which is promoted by substituents in ortho and para positions. These results are consistent with experimental data and could be used to propose point mutations that allow this enzyme to process new molecules of biotechnological interest.