Carlos H.T.,Metropolitan University of Educational Sciences
Journal of the Chilean Chemical Society | Year: 2016
Based on a thermodynamic cycle the pKa in aqueous phase of the series of molecules of the type (Me)2-N-Phenyl-(HC=CH)n-CHO with n = 0, 1, 2 and 3 have been determined. To that end the SM5.4 solvation model has been considered. The calculated pKa have been compared with the pKa measured experimentally. A study has also been made of the proton affinity in the gas phase and in aqueous phase. The calculation scheme agrees favorably, in a qualitative manner, considering favorably the molecular and solute-solvent interaction characteristics that determine the free energy that governs the acid-base properties of the molecules in the series.
Flores-Prado L.,Metropolitan University of Educational Sciences |
Niemeyer H.M.,University of Chile
Neotropical Entomology | Year: 2012
Parasitoid fitness depends on the ability of females to locate a host. In some species of Ichneumonoidea, female parasitoids detect potential hosts through vibratory cues emanating from them or through vibrational sounding produced by antennal tapping on the substrate. In this study, we (1) describe host location behaviors in Grotea gayi Spinola (Hymenoptera: Ichneumonidae) and Labena sp. on nests of Manuelia postica Spinola (Hymenoptera: Apidae), (2) compare nest dimensions between parasitized and unparasitized nests, (3) correlate the length of M. postica nests with the number of immature individuals developing, and (4) establish the relative proportion of parasitized nests along the breeding period of M. postica. Based on our results, we propose that these parasitoids use vibrational sounding as a host location mechanism and that they are able to assess host nest dimensions and choose those which may provide them with a higher fitness. Finally, we discuss an ancestral host-parasitoid relationship between Manuelia and ichneumonid species. © 2012 Sociedade Entomológica do Brasil.
Osorio-Fuentealba C.,Metropolitan University of Educational Sciences |
Osorio-Fuentealba C.,Hospital for Sick Children |
Klip A.,Hospital for Sick Children
Biochemical Journal | Year: 2015
The serine/threonine kinase Akt/PKB (protein kinase B) is key for mammalian cell growth, survival, metabolism and oncogenic transformation. The diverse level and tissue expression of its three isoforms, Akt1/PKBα, Akt2/PKBβ and Akt3/PKBγ , make it daunting to identify isoform-specific actions in vivo and even in isolated tissues/cells. To date, isoform-specific knockout and knockdown have been the best strategies to dissect their individual overall functions. In a recent article in the Biochemical Journal, Kajno et al. reported a new strategy to study isoform selectivity in cell lines. Individual Akt/PKB isoforms in 3T3-L1 pre-adipocytes are first silenced via shRNA and stable cellular clones lacking one or the other isoform are selected. The stably silenced isoform is then replaced by a mutant engineered to be refractory to inhibition by MK-2206 (Akt1W80A or Akt2W80A). Akt1W80A or Akt2W80A are functional and effectively recruited to the plasma membrane in response to insulin. The system affords the opportunity to acutely control the activity of the endogenous non-silenced isoform through timely addition of MK-2206. Using this approach, it is confirmed that Akt1/PKBα is the preferred isoform sustaining adipocyte differentiation, but both Akt1/PKBα and Akt2/PKBβ can indistinctly support insulin-dependent FoxO1 (forkhead box O1) nuclear exclusion. Surprisingly, either isoform can also support insulin-dependent glucose transporter (GLUT) 4 translocation to the membrane, in contrast with the preferential role of Akt2/ PKBβ assessed by knockdown studies. The new strategy should allow analysis of the plurality of Akt/PKB functions in other cells and in response to other stimuli. It should also be amenable to high-throughput studies to speed up advances in signal transmission by this pivotal kinase. © 2015 Authors; published by Portland Press Limited.
Cassels B.K.,University of Chile |
Asencio M.,University of Chile |
Asencio M.,Metropolitan University of Educational Sciences
Phytochemistry Reviews | Year: 2011
The continued advance of HIV-AIDS makes the development of relatively inexpensive, freely accessible, and mechanistically more diverse antiviral therapies an urgent need. Natural products are, directly or indirectly, an important potential source of compounds meeting these conditions. A review of the recent literature indicates that some hemisynthetic triterpenoid derivatives, particularly belonging to the lupane, oleanane and ursane series, may be nearing a stage where they can be used to complement existing therapeutic approaches. On the other hand, although some natural derivatives of tetracyclic terpenoid families have revealed many novel structures and some promise as anti-HIV substances, their chemical modification to improve their potency and selectivity remains practically untouched. While ongoing work with the more 'classical' pentacyclic triterpenoids will continue to be a fertile field for HIV-AIDS drug discovery, the other structural groups offer unprecedented opportunities for the development of additional substances with useful properties and for the discovery of novel targets for antiviral therapy. © Springer Science+Business Media B.V. 2010.
Patricia Estrada M.,Metropolitan University of Educational Sciences
Zootaxa | Year: 2016
The species of the genus Arthrobrachus Solier, 1849 distributed in Argentina, Bolivia, Paraguay and Uruguay have been revised. The morphological study of specimens and the review of the type material have resulted in a new combination: Arthrobrachus flavomarginatus (Blanchard, 1843) n. comb. (from Astylus Laporte, 1836), and four new synonymies: Arthrobrachus rufitarsis Philippi & Philippi, 1864 = A. obscuripes Pic, 1927 n. syn.; Arthrobrachus flavomarginatus (Blanchard, 1843) = A. xanthurus (Blanchard, 1843) n. syn. = A. boucardi Pic, 1919 n. syn. = A. lajoyei Pic, 1919 n. syn. Three species described by Steinheil (1874), Arthrobrachus depressus, Arthrobrachus testaceolimbatus and Arthrobrachus testaceus are considered as incertae sedis and Arthrobrachus quadrilineatus Steinheil, 1874 is transferred to Astylus Laporte, 1836 as A. steinheili nomen novum. Four new species of Arthrobrachus have been described: A. antonioi n. sp., A. eloisae n. sp., A. solervicensi n. sp. and A. armandoi n. sp. Distributional data and a key to the species are provided. © Copyright 2016 Magnolia Press.
Flores-Prado L.,Metropolitan University of Educational Sciences
Revista Chilena de Historia Natural | Year: 2012
The levels of sociality in Hymenoptera have been associated with key behavioural traits, such as nesting and agonistic behaviour, and intraspecifi c recognition capacity. Nestmate recognition is a widespread condition among eusocial species, and can be inferred from the outcome of the interaction between females from the same or different nests; females are more tolerant towards nestmate than towards non-nestmate females. By contrast, in most solitary species females are aggressive towards conspecifi c females. In eusocial species, food for immature brood is directly provided by the mother or by workers; thus, the frequent contact of the brood with nursing adults may help our understanding of social recognition behaviours. At the other extreme, females in solitary species construct nests that do not allow physical interaction between adult and immature individuals. Despite this, recent studies suggest that self-referencing may contribute to overcoming the lack of stimulation with conspecifi c cues, and perhaps corresponds to the starting point in the development and evolution of sociality. The Xylocopinae (Apidae) subfamily has emerged as a valuable model to study the transitions in social evolution because it contains species ranging from solitary to eusocial. The tribe Manueliini represents an interesting taxon in the study of the evolution of sociality in Xylocopinae because it has been hypothesized as the sister group of all other Xylocopinae. It is a relictual taxon retaining several ancestral morphological features and contains only largely solitary species (although nestmate and kin recognition has been recently demonstrated in one of these species), and some species exhibit behavioural traits that have been proposed as prerequisite for the evolution to social life. In this work, the degrees of sociality associated with behavioural traits are reviewed in Hymenoptera, the hypothetical evolutionary routes, origins and losses of highly social behaviour are discussed, and information about taxonomic groups that have emerged as valuable models to study the evolution of sociality is reported. Additionally, features proposed as precursors of sociality are compared within the subfamily Xylocopinae, evidence demonstrating nestmate recognition in a Manueliini species, a phenomenon fi rst demonstrated in a largely solitary species, is discussed, and the evolution of sociality associated with behavioural traits is analyzed, on the basis of a new phylogenetic hypothesis for the Xylocopinae. © Sociedad de Biología de Chile.
Chiu K.-S.,Metropolitan University of Educational Sciences
The Scientific World Journal | Year: 2014
We investigate the existence of the periodic solutions of a nonlinear integro-differential system with piecewise alternately advanced and retarded argument of generalized type, in short DEPCAG; that is, the argument is a general step function. We consider the critical case, when associated linear homogeneous system admits nontrivial periodic solutions. Criteria of existence of periodic solutions of such equations are obtained. In the process we use Green's function for periodic solutions and convert the given DEPCAG into an equivalent integral equation. Then we construct appropriate mappings and employ Krasnoselskii's fixed point theorem to show the existence of a periodic solution of this type of nonlinear differential equations. We also use the contraction mapping principle to show the existence of a unique periodic solution. Appropriate examples are given to show the feasibility of our results. © 2014 Kuo-Shou Chiu.
Cardenas-Jiron G.I.,University of Santiago de Chile |
Gonzalez C.,Metropolitan University of Educational Sciences |
Benavides J.,University of Santiago de Chile
Journal of Physical Chemistry C | Year: 2012
The oxidation of nitric oxide (NO) mediated by substituted nickel phthalocyanines (NiPc(X) n) has been investigated for 19 complexes at the B3LYP and M05-2X/LANL2DZ/6-31G(d) levels of theory. Unimolecular reactivity descriptors like chemical potential and electrophilicity were calculated for NiPc(X) n, giving an account of the substituent effect and indicating that electron-withdrawing groups favor the reduction of NiPc(X) n. Bimolecular reactivity descriptor as donor-acceptor hardness was used to get information about the affinity of NO by NiPc(X) n and suggests that Ni(III) has better affinity than Ni(II). A mechanism where Ni(III) catalyzes the oxidation of NO instead of Ni(II) was proposed. Optimized molecular structures calculated for the NO⋯NiPc(X) n adducts confirm that a larger charge transfer occurs from NO to Ni(III)Pc(X) n in comparison with Ni(II)Pc(X) n and that the reduction in the former complexes happens on the phthalocyanine ligand. © 2012 American Chemical Society.
Frias-Lasserre D.,Metropolitan University of Educational Sciences
Neotropical Entomology | Year: 2010
In the present study, the morphology, color pattern, chromosomal complement and aspects of meiosis in natural populations at the borders of the distributions of Mepraia gajardoi Frías et al and Mepraia spinolai (Porter) are described. The males of these bordering populations are brachypterous or macropterous, while females are always micropterous. Morphological and cytogenetic data indicated that the populations that border the distributions of M. gajardoi and M. spinolai, belong to a different species of parapatric origin.
Frias-Lasserre D.,Metropolitan University of Educational Sciences
International Journal of Molecular Sciences | Year: 2012
The origin of genes is one of the most enigmatic events in the origin of life. It has been suggested that noncoding (nc) RNA was probably a precursor in the formation of the first polypeptide, and also at the origin of the first manifestation of life and genes. ncRNAs are also becoming central for understanding gene expression and silencing. Indeed, before the discovery of ncRNAs, proteins were viewed as the major molecules in the regulation of gene expression and gene silencing; however, recent findings suggest that ncRNA also plays an important role in gene expression. Reverse transcription of RNA viruses and their integration into the genome of eukaryotes and also their relationship with the ncRNA suggest that their origin is basal in genome evolution, and also probably constitute the first mechanism of gene regulation. I am to review the different roles of ncRNAs in the framework of gene evolution, as well as the importance of ncRNAs and viruses in the epigenesis and in the non-Mendelian model of heredity and evolution. © 2012 by the authors; licensee MDPI, Basel, Switzerland.