G protein beta gamma subunits synthesized in Sf9 cells. Functional characterization and the significance of prenylation of gamma

Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) consist of a nucleotide-binding alpha subunit and a high- affinity complex of beta and gamma subunits. There is molecular heterogeneity of beta and gamma, but the significance of this diversity is poorly understood. Different G protein beta and gamma subunits have been expressed both singly and in combinations in Sf9 cells. Although expression of individual subunits is achieved in all cases, beta gamma subunit activity (support of pertussis toxin-catalyzed ADP-ribosylation of rGi alpha 1) is detected only when beta and gamma are expressed concurrently. Of the six combinations of beta gamma tested (beta 1 or beta 2 with gamma 1, gamma 2, or gamma 3), only one, beta 2 gamma 1, failed to generate a functional complex. Each of the other five complexes has been purified by subunit exchange chromatography using Go alpha-agarose as the chromatographic matrix. We have detected differences in the abilities of the purified proteins to support ADP- ribosylation of Gi alpha 1; these differences are attributable to the gamma component of the complex. When assayed for their ability to inhibit calmodulin-stimulated type-I adenylylcyclase activity or to potentiate Gs alpha-stimulated type-II adenylylcyclase, recombinant beta 1 gamma 1 and transducin beta gamma are approximately 10 and 20 times less potent, respectively, than the other complexes examined. Prenylation and/or further carboxyl-terminal processing of gamma are not required for assembly of the beta gamma subunit complex but are indispensable for high affinity interactions of beta gamma with either G protein alpha subunits or adenylylcyclases

Origin of nonlinear magnetoelectric response in rare-earth orthoferrite perovskite oxides

We report a theoretical study of the non-linear magnetoelectric response of GdFeO$_3$ through an analytical approach combined with a Heisenberg model which is fitted against first-principles calculations. Our theory reproduces the non-linear change of polarization under applied magnetic field reported experimentally such that it allows to analyze the origin of the large responses in the different directions. We show that the non-linear character of the response in these materials originates from the fact that the antiferromagnetic order of Gd atoms changes non-linearly with respect to the applied magnetic field. Our model can be generalized to other materials in which the antiferromagnetic ordering breaks inversion symmetry

Giant Electrophononic Response in PbTiO3 by Strain Engineering

We demonstrate theoretically how, by imposing epitaxial strain in a ferroelectric perovskite, it is possible to achieve a dynamical control of phonon propagation by means of external electric fields, which yields a giant electrophononic response, i.e., the dependence of the lattice thermal conductivity on external electric fields. Specifically, we study the strain-induced manipulation of the lattice structure and analyze its interplay with the electrophononic response. We show that tensile biaxial strain can drive the system to a regime where the electrical polarization can be effortlessly rotated and thus yield giant electrophononic responses that are at least one order of magnitude larger than in the unstrained system. These results derive directly from the almost divergent behavior of the electrical susceptibility at those critical strains that drive the polarization on the verge of a spontaneous rotation.Peer reviewe

Anisotropy-driven thermal conductivity switching and thermal hysteresis in a ferroelectric

Peer reviewe

El tiempo de desplazamiento y su efecto en indicadores de la calidad de vida rural: un estudio en el municipio de Salinas, San Luis Potosí, México

El uso de los bienes públicos por parte de las autoridades que gobiernan una región delimitada administrativamente es uno de los problemas enfrentados por las sociedades, incluyendo las rurales. Una red de caminos rurales es un ejemplo de bienes con escaso mantenimiento por parte de la autoridad, además de ser la vía de flujo de bienes y servicios. Su buen estado y mantenimiento es un factor que influencia el desarrollo rural. En esta investigación se analiza el efecto de los caminos rurales en indicadores sociales relacionados con la calidad de vida de una población rural. Se estimó el tiempo de desplazamiento de las comunidades hacia la cabecera municipal como medida de alejamiento de los servicios; se revisaron indicadores indirectos sobre marginación, electrificación, y niveles de educación bá- sica, así como efectos directos en el ingreso económico, gasto familiar y condiciones escolares con que cuentan las familias rurales debido al estado de los caminos. La marginación y la electrificación no mostraron dependencia con el alejamiento; sin embargo se identificó un menor aprovechamiento escolar en los planteles fuera de la cabecera municipal, además de que el ingreso familiar se reduce hasta en 40% conforme aumenta el tiempo de desplazamiento

Priorización Ejidal De Criterios Sobre Bienes Públicos: El Caso De Caminos Rurales

En este artículo se fijó como objetivo definir las preferencias de la población sobre el mantenimiento de los caminos rurales como vías de flujo de bienes y servicios que usan cotidianamente, para ello se presenta un modelo de participación de la sociedad rural donde se integra la opinión de los beneficiarios en el mantenimiento de los caminos rurales basado en un proceso de análisis jerárquico que valora la importancia de criterios económicos, sociales y ambientale

Universal temporal features of rankings in competitive sports and games

Many complex phenomena, from the selection of traits in biological systems to hierarchy formation in social and economic entities, show signs of competition and heterogeneous performance in the temporal evolution of their components, which may eventually lead to stratified structures such as the wealth distribution worldwide. However, it is still unclear whether the road to hierarchical complexity is determined by the particularities of each phenomena, or if there are universal mechanisms of stratification common to many systems. Human sports and games, with their (varied but simplified) rules of competition and measures of performance, serve as an ideal test bed to look for universal features of hierarchy formation. With this goal in mind, we analyse here the behaviour of players and team rankings over time for several sports and games. Even though, for a given time, the distribution of performance ranks varies across activities, we find statistical regularities in the dynamics of ranks. Specifically the rank diversity, a measure of the number of elements occupying a given rank over a length of time, has the same functional form in sports and games as in languages, another system where competition is determined by the use or disuse of grammatical structures. Our results support the notion that hierarchical phenomena may be driven by the same underlying mechanisms of rank formation, regardless of the nature of their components. Moreover, such regularities can in principle be used to predict lifetimes of rank occupancy, thus increasing our ability to forecast stratification in the presence of competition