http://dspace.utalca.cl/handle/1950/1411 Search the Channel search http://dspace.utalca.cl/simple-search http://dspace.utalca.cl/handle/1950/9171 Title: K+ Conduction and Mg2+ Blockade in a Shaker Kv-Channel Single Point Mutant with an Unusually High Conductance<br/><br/>Authors: Moscoso, C.; Vergara-Jaque, A.; Marquez-Miranda, V.; Sepulveda, R.V.; Valencia, I.; Diaz-Franulic, I.; Gonzalez-Nilo, F.; Naranjo, D.<br/><br/>Abstract: Potassium channels exhibit a large diversity of single-channel conductances. Shaker is a low-conductance K-channel in which Pro475 -> Asp, a single-point mutation near the internal pore entrance, promotes 6- to 8-fold higher unitary current. To assess the mechanism for this higher conductance, we measured Shaker-P475D single-channel current in a wide range of symmetrical K+ concentrations and voltages. Below 300 mM K+, the current-to-voltage relations (i-V) showed inward rectification that disappeared at 1000 mM K+. Single-channel conductance reached a maximum of similar to 190 pS at saturating [K+], a value 4- to 5-fold larger than that estimated for the native channel. Intracellular Mg2+ blocked this variant with similar to 100-fold higher affinity. Near zero voltage, blockade was competitively antagonized by K+; however, at voltages >100 mV, it was enhanced by K+. This result is consistent with a lock-in effect in a single-file diffusion regime of Mg2+ and K+ along the pore. Molecular-dynamics simulations revealed higher K+ density in the pore, especially near the Asp-475 side chains, as in the high-conductance MthK bacterial channel. The molecular dynamics also showed that K+ ions bound distally can coexist with other K+ or Mg2+ in the cavity, supporting a lock-in mechanism. The maximal K+ transport rate and higher occupancy could be due to a decrease in the electrostatic energy profile for K+ throughout the pore, reducing the energy wells and barriers differentially by similar to 0.7 and similar to 2 kT, respectively.<br/><br/>Description: Vergara-Jaque, A (Vergara-Jaque, Ariela). Univ Talca, Ctr Bioinformat & Simulac Mol, Talca, Chile http://dspace.utalca.cl/handle/1950/9170 Title: Social psychology predictors for the adoption of soil conservation measures in Central Chile<br/><br/>Authors: Huenchuleo, C.; Barkmann, J.; Villalobos, P.<br/><br/>Abstract: With low adoption rates of soil conservation measures (SCM) widespread, we examine determinants of current and potential future adoption in the Secano Costero region of Central Chile. Randomly selected farmers (N?=?140) spent an equivalent of 48?000 CLP/year ( 79 US$) on SCM. Contingent valuation of a hypothesized soil conservation programme revealed a willingness-to-pay of 30?610 CLP/year ( 50.4 US$) for future adoption. Social-psychology variables from Protection Motivation Theory (PMT; response efficacy, perceived barriers) were used to predict current and potential future adoption. Current spending on SCM is influenced by perceptions of (1) erosion problem severity, (2) response efficacy of SCM, (3) farming problems and (4) barriers (lack of labour and draught animals). In addition, farm size and education were significant predictors. Willingness-to-pay for future adoption of SCM is influenced by farmer perception of (1) response efficacy of SCM, and (2) community support to the programme as well as farm size, age and gender. Our results suggest that formal psychometric scale development for social-psychology predictors for the adoption of SCM, e.g. based on PMT, is a promising avenue for the analysis of soil conservation decisions. Copyright (c) 2011 John Wiley & Sons, Ltd.<br/><br/>Description: Villalobos, P (Villalobos, P.). Univ Talca, Talca 3460000, Chile. http://dspace.utalca.cl/handle/1950/9169 Title: Phenolic Constituents of the Chilean Herbal Tea Fabiana imbricata R. et P.<br/><br/>Authors: Quispe, C.; Viveros-Valdez, E.; Schmeda-Hirschmann, G.<br/><br/>Abstract: "Pichi" or "pichi romero" (Fabiana imbricata R. et. P., Solanaceae) is a Chilean plant used as a tea in the Andean regions of Chile and Argentina. A very simple and direct method was developed for the qualitative analysis of polyphenols in the tea by high-performance liquid chromatography (HPLC) with diode array detection and electrospray ionization tandem mass spectrometry. The phenolic constituents identified in the teas were chlorogenic acid (3-O-caffeoylquinic acid), p-hydroxyacetophenone, scopoletin and quercetin derivatives. The glycosides were mainly glucosides from p-hydroxyacetophenone and scopoletin while di- and tri-glycosides from quercetin were the main flavonoids. The content of the main phenolic compounds in the teas (g/100 g lyophilized infusion) was 0.8-1.9 % for scopoletin, 0.4-6.2 % for p-hydroxyacetophenone and 2.1-4.3 % for rutin, respectively. The health-promoting properties reported for this herbal tea can be associated with the presence of several phenolics with known antioxidant, diuretic and antiinflammatory activity.<br/><br/>Description: Schmeda-Hirschmann, G (reprint author), Univ Talca, Inst Quim Recursos Nat, Lab Quim Prod Nat, Casilla 747, Talca, Chile. http://dspace.utalca.cl/handle/1950/9168 Title: Biological Activity of Isoflavonoids from Azorella madreporica<br/><br/>Authors: Quesada, L.; Areche, C.; Astudillo, L.; Gutierrez, M.; Sepulveda, B.; San-Martin, A.<br/><br/>Abstract: Four isoflavones, isolated from the whole plant of Azurella madreporica, were identified as angustone C (1), alpinumisoflavone (2), licoisoflavone A (3) and isolupalbigenin (4) by spectroscopic studies. The compounds were evaluated for antibacterial and gastroprotective activities. This is the first time that isoflavonoids have been reported in this genus.<br/><br/>Description: Quesada, L (Quesada, Luisa); Astudillo, L (Astudillo, Luis); Gutierrez, M (Gutierrez, Margarita). Univ Talca, Inst Quim Recursos Nat, Talca, Chile .