Molecular mechanism of protein-retinal coupling in bacteriorhodopsin.

Bacteriorhodopsin is a membrane protein that functions as a light-driven proton pump. Each cycle of proton transport is initiated by the light-induced isomerization of retinal from the all-trans to 13-cis configuration and is completed by the protein-driven reisomerization of retinal to the all-trans configuration. Previous studies have shown that replacement of Leu-93, a residue in close proximity to the 13-methyl group of retinal, by alanine, resulted in a 250-fold increase in the time required to complete each photocycle. Here, we show that the kinetic defect in the photocycle of the Leu-93-->Ala mutant occurs at a stage after the completion of proton transport and can be overcome in the presence of strong background illumination. Time-resolved retinal-extraction experiments demonstrate the continued presence of a 13-cis intermediate in the photocycle of the Leu-93-->Ala mutant well after the completion of proton release and uptake. These results indicate that retinal reisomerization is kinetically the rate-limiting step in the photocycle of this mutant and that the slow thermal reisomerization can be bypassed by the absorption of a second photon. The effects observed for the Leu-93-->Ala mutant are not observed upon replacement of any other residue in van der Waals contact with retinal or upon replacement of Leu-93 by valine. We conclude that the contact between Leu-93 and the 13-methyl group of retinal plays a key role in controlling the rate of protein conformational changes associated with retinal reisomerization and return of the protein to the initial state.

La situación de la música clásica en España: de la transición a la actualidad

La Sociología de la Música clásica en España es un amplio campo de conocimiento, y lo es en varios sentidos. De una parte, es un objeto de investigación novedoso; y por otro, y como consecuencia de lo anterior, hay pocos investigadores trabajando en la materia, a pesar de que algunos de los grandes sociólogos ya prestaron atención al arte y más específicamente a la música (como Weber (1977), Simmel (2003), Durkheim (2002), Bourdieu (2004, 2005, 2008), etc.). Actualmente, la Sociología de la Música es una disciplina en desarrollo que ofrece un interesante y atractivo campo de investigación. Este trabajo trata de contribuir al conocimiento de esta disciplina, describiendo las principales líneas que dibujan la situación de la música en España a lo largo del siglo XX, circunscrito al ámbito de la música clásica. Para España, el siglo XX contiene importante hitos políticos que tienen consecuencias en todos los niveles de la vida social: político, económico, social, cultural y también musical. El principal objetivo de esta investigación es encontrar las causas de la situación actual, cuáles son los factores que nos han llevado a este estado, cuáles son las debilidades, los puntos fuertes, en qué sentidos podemos mejorar, etc. Para sumergirnos en esta realidad se han utilizado diferentes metodologías que permiten un mejor y mayor acercamiento a nuestro objeto de estudio. El cuerpo de la investigación está dividido en cinco capítulos. El primer capítulo está dedicado a la introducción; en el que se hace un resumen de los principales autores y tendencias en Sociología de la Música...

Serological diagnosis of echinococcosis: the diagnostic potential of native antigens

PURPOSE: Human alveolar (AE) and cystic echinococcosis (CE) caused by the metacestode stages of Echinococcus multilocularis and E. granulosus, respectively, lack pathognomonic clinical signs. Diagnosis therefore relies on the results of imaging and serological studies. The primary goal of this study was to evaluate the efficacy of several easy-to-produce crude or partially purified E. granulosus and E. multilocularis metacestode-derived antigens as tools for the serological diagnosis and differential diagnosis of patients suspicious for AE or CE. METHODS: The sera of 51 treatment-naïve AE and 32 CE patients, 98 Swiss blood donors and 38 patients who were initially suspicious for echinococcosis but suffering from various other liver diseases (e.g., liver neoplasia, etc.) were analysed. RESULTS: According to the results of enzyme-linked immunosorbent assays (ELISA), metacestode-derived antigens of E. granulosus had sensitivities varying from 81 to 97% and >99.9% for the diagnosis of CE and AE, respectively. Antigens derived from E. multilocularis metacestodes had sensitivities ranging from 84 to 91% and >99.9% for the diagnosis of CE and AE, respectively. Specificities ranged from 92 to >99.9%. Post-test probabilities for the differential diagnosis of AE from liver neoplasias, CE from cystic liver lesions, and screening for AE in Switzerland were around 95, 86 and 2.2%, respectively. Cross-reactions with antibodies in sera of patients with other parasitic affections (fasciolosis, schistosomosis, amebosis, cysticercosis, and filarioses) did occur at variable frequencies, but could be eliminated through the use of confirmatory testing. CONCLUSIONS: Different metacestode-derived antigens of E. granulosus and E. multilocularis are valuable, widely accessible, and cost-efficient tools for the serological diagnosis of echinococcosis. However, confirmatory testing is necessary, due to the lack of species specificity and the occurrence of cross-reactions to other helminthic diseases.

The Effectiveness of Firms' Strategic Orientations: Investigating Multiple Theoretical Perspectives

The strategic orientation of firms can take on many forms. Researchers most commonly distinguish between entrepreneurial, market, and learning orientations. In combination, strategic orientations represent a firm's value proposition in terms of the markets in which it operates, where it deploys its resources, and which behavioral patterns are established. This thesis provides insights into the effectiveness of strategic orientations by adopting multiple theoretical perspectives. The strategic orientations of entrepreneurial, market, learning, and innovation orientations are investigated in an isolated as well as interrelated manner. The first research article concentrates on entrepreneurial orientation as its conceptualization and operationalization is subject to several debates in the literature. This conceptual study shows how the challenges of the entrepreneurial orientation construct can be overcome in future research to arrive at a higher level of construct clarity. Thereby, the theoretical perspectives of entrepreneurial dominant logic and the theory of planned behavior are employed. The literature has predominantly focused on investigating the effectiveness of particular strategic orientations. Recently, scholars have stressed their synergetic impact on firm performance and, as such, the relevance of considering their combined role in creating superior value for firms. However, empirical research on their interrelatedness remains scant and dispersed, making it necessary to conduct further research on strategic orientations in an integrative manner. As such, the second research article demonstrates which interrelated roles are played by entrepreneurial, market, and learning orientations in their relationship to firm performance. The rich body of existing knowledge is synthesized by means of meta-analysis under the perspective of strategic coalignment as well as the resource-based view of the firm.

Advanced public transportation systems: the state of the art update '98.

Federal Transit Administration, Washington, D.C.

Advanced public transportation systems: the state of the art update '94. Final report.

Federal Transit Administration, Washington, D.C.

Da oceano a oceano; descrizione dell' oceano e della sua vita.

Mode of access: Internet.

Review of and preliminary guidelines for integrating transit into transportation management centers. Final report.

Transportation Systems Center, Cambridge, Mass.

Historiae Societatis Jesu prouinciae Bohemiae : Pars primae ab anno Christi MDLV ad annum MDXCII /

Mode of access: Internet.

Quaestionum Vergilianarum criticarum specimen ...

Inaug.-Diss.--Göttingen.

Quaestiones Livianae. Progr.

Mode of access: Internet.