Membrane interaction of polymyxin B and synthetic analogues studied in biomimetic systems: implications for antibacterial action

Membrane-active antimicrobial peptides, such as polymyxin B (PxB), are currently in the spotlight as potential candidates toovercome bacterial resistance. We have designed synthetic analogs ofPxB in order to determine the structural requirements for membraneaction. Since the mechanism of action of PxB involves interaction withboth the outer membrane and the cytoplasmic membrane of Gramnegative bacteria, we have used an approach based on mimicking theouter layers of these membranes using monolayers, Langmuir-Blodgettfilms and unilamelar vesicles, and applying a battery of biophysicalmethods in order to dissect the different events of membraneinteraction. Collectively, results indicate that the PxB analogues act inthe bacterial membrane by the same mechanism than PxB, and that cationic amphipathicity determines peptide activity.

Functional interaction between peroxisome proliferator-activated receptors-alpha and Mef-2C on human carnitine palmitoyltransferase 1beta (CPT1beta) gene activation

Muscle-type carnitine palmitoyltransferase 1 (CPT1β) is considered to be the gene that controls fatty acid mitochondrial β-oxidation. A functional peroxisome proliferator-activated receptor (PPAR) responsive element (PPRE) and a myocite-specific (MEF2) site that binds MEF2A and MEF2C in the promoter of this gene had been previously identified. We investigated the roles of the PPRE and the MEF2 binding sites and the potential interaction between PPARα and MEF2C regulating the CPT1β gene promoter. Mutation analysis indicated that the MEF2 site contributed to the activation of the CPT1β promoter by PPAR in C2C12 cells. The reporter construct containing the PPRE and the MEF2C site was synergistically activated by co-expression of PPAR, retinoid X receptor (RXR) and MEF2C in non-muscle cells. Moreover, protein-binding assays demonstrated that MEF2C and PPAR specifically bound to one another in vitro. Also for the synergistic activation of the CPT1β gene promoter by MEF2C and PPARα-RXRα, a precise arrangement of its binding sites was essential.

Membrane interaction of polymyxin B and synthetic analogues studied in biomimetic systems: implications for antibacterial action

Membrane-active antimicrobial peptides, such as polymyxin B (PxB), are currently in the spotlight as potential candidates toovercome bacterial resistance. We have designed synthetic analogs ofPxB in order to determine the structural requirements for membraneaction. Since the mechanism of action of PxB involves interaction withboth the outer membrane and the cytoplasmic membrane of Gramnegative bacteria, we have used an approach based on mimicking theouter layers of these membranes using monolayers, Langmuir-Blodgettfilms and unilamelar vesicles, and applying a battery of biophysicalmethods in order to dissect the different events of membraneinteraction. Collectively, results indicate that the PxB analogues act inthe bacterial membrane by the same mechanism than PxB, and that cationic amphipathicity determines peptide activity.

The Conservativeness of the Central Bank when Institutional Quality is Poor

We propose an extension of Alesina and Tabellini 's model (1987) to include corruption, which is understood as the presence of weak institutions collecting revenue through formal tax channels. This paper analyses how conservative should an independent central bank be when the institutional quality is poor. When there are no political distortions, we show that the central bank has to be more conservative than the government, except with complete corruption. In this particular case, the central bank should be as conservative as the government. Further, we obtain that the relationship between the optimal relative degree of conservativeness of the central bank and the degree of corruption is affected by supply shocks. Concretely, when these shocks are not important, the central bank should be less conservative if the degree of corruption increases. However, this result may not hold when the shocks are relevant. JEL classi fication: D6, D73, E52, E58, E62, E63. Keywords: Central Bank Conservativeness; Corruption; Fiscal Policy; Monetary Policy; Seigniorage.

Do protein–protein interaction databases identify moonlighting proteins?

One of the most striking results of the human (and mammalian) genomes is the low number of protein-coding genes. To-date, the main molecular mechanism to increase the number of different protein isoforms and functions is alternative splicing. However, a less-known way to increase the number of protein functions is the existence of multifunctional, multitask, or ‘‘moonlighting’’, proteins. By and large, moonlighting proteins are experimentally disclosed by serendipity. Proteomics is becoming one of the very active areas of biomedical research, which permits researchers to identify previously unseen connections among proteins and pathways. In principle, protein–protein interaction (PPI) databases should contain information on moonlighting proteins and could provide suggestions to further analysis in order to prove the multifunctionality. As far as we know, nobody has verified whether PPI databases actually disclose moonlighting proteins. In the present work we check whether well-established moonlighting proteins present in PPI databases connect with their known partners and, therefore, a careful inspection of these databases could help to suggest their different functions. The results of our research suggest that PPI databases could be a valuable tool to suggest multifunctionality.

Gene Promoter Evolution Targets the Center of the Human Protein Interaction Network

Assessing the contribution of promoters and coding sequences to gene evolution is an important step toward discovering the major genetic determinants of human evolution. Many specific examples have revealed the evolutionary importance of cis-regulatory regions. However, the relative contribution of regulatory and coding regions to the evolutionary process and whether systemic factors differentially influence their evolution remains unclear. To address these questions, we carried out an analysis at the genome scale to identify signatures of positive selection in human proximal promoters. Next, we examined whether genes with positively selected promoters (Prom+ genes) show systemic differences with respect to a set of genes with positively selected protein-coding regions (Cod+ genes). We found that the number of genes in each set was not significantly different (8.1% and 8.5%, respectively). Furthermore, a functional analysis showed that, in both cases, positive selection affects almost all biological processes and only a few genes of each group are located in enriched categories, indicating that promoters and coding regions are not evolutionarily specialized with respect to gene function. On the other hand, we show that the topology of the human protein network has a different influence on the molecular evolution of proximal promoters and coding regions. Notably, Prom+ genes have an unexpectedly high centrality when compared with a reference distribution (P = 0.008, for Eigenvalue centrality). Moreover, the frequency of Prom+ genes increases from the periphery to the center of the protein network (P = 0.02, for the logistic regression coefficient). This means that gene centrality does not constrain the evolution of proximal promoters, unlike the case with coding regions, and further indicates that the evolution of proximal promoters is more efficient in the center of the protein network than in the periphery. These results show that proximal promoters have had a systemic contribution to human evolution by increasing the participation of central genes in the evolutionary process.

Interaction of Spiral Waves in the Complex Ginzburg-Landau Equation

Solutions of the general cubic complex Ginzburg-Landau equation comprising multiple spiral waves are considered, and laws of motion for the centers are derived. The direction of the motion changes from along the line of centers to perpendicular to the line of centers as the separation increases, with the strength of the interaction algebraic at small separations and exponentially small at large separations. The corresponding asymptotic wave number and frequency are also determined, which evolve slowly as the spirals move

O2, the Oberta in Open Access : institutional repository

Tríptic informatiu sobre la publicació de documents amb accés obert en el repositori institucional de la UOC, O2 (La Oberta en obert). Aquest informa sobre quins documents hi poden publicar els membres de la comunitat UOC, com fer-ho i els serveis de valor afegit per a tots els usuaris (web 2.0, subscripció per RSS o correu electrònic, exportació al gestor bibliogràfic Refworks, etc.) i per a la recerca (lligam amb l'aplicació d'avaluació de la recerca GIR i informació del factor d'impacte de la revista a SCOPUS, IN-RECS/IN-RECJ i MIAR).

Technology educational affordance: Bridging the gap between patterns of interaction and technology usage

Peer-reviewed

From institutional repositories to personal collections of learning resources

Institutional digital repositories are a basic piece to provide preservation and reutilization of learning resources. However, their creation and maintenance is usually performed following a top-down approach, causing limitations in the search and reutilization of learning resources. In order to avoid this problem we propose to use web 2.0 functionalities. In this paper we present how tagging can be used to enhance the search and reusability functionalities of institutional learning repositories as well as promoting their usage. The paper also describes the evaluation process that was performed in a pilot experience involving open educational resources.

Binary proposal for assessing quality of Open Access Institutional Repositories : the case of Spanish repositories

The reason for this study is to propose a new quantitative approach on how to assess the quality of Open Access University Institutional Repositories. The results of this new approach are tested in the Spanish University Repositories. The assessment method is based in a binary codification of a proposal of features that objectively describes the repositories. The purposes of this method are assessing the quality and an almost automatically system for updating the data of the characteristics. First of all a database was created with the 38 Spanish institutional repositories. The variables of analysis are presented and explained either if they are coming from bibliography or are a set of new variables. Among the characteristics analyzed are the features of the software, the services of the repository, the features of the information system, the Internet visibility and the licenses of use. Results from Spanish universities ARE provided as a practical example of the assessment and for having a picture of the state of the development of the open access movement in Spain.

A survey on automatic recommenders in the context of institutional repositories

Peer-reviewed

Building a usable and accessible semantic web interaction platform

Semantic Web applications take off is being slower than expected, at least with respect to “real-world” applications and users. One of the main reasons for this lack of adoption is that most Semantic Web user interfaces are still immature from the usability and accessibility points of view. This is due to the novelty of these technologies, but this also motivates the exploration of alternative interaction paradigms, different from the “traditional” Web or Desktop applications ones. Our proposal is realized in the Rhizomer platform, which explores the possibilities of the object–action interaction paradigm at the Web scale. This paradigm is well suited for heterogeneous resource spaces such as those common in the Semantic Web. Resources, described by metadata, correspond to the objects in the paradigm. Semantic web services, which are dynamically associated to these objects, correspond to the actions. The platform is being put into practice in the context of a research project in order to build an open application for media distribution based on Semantic Web technologies. Moreover, its usability and accessibility have been evaluated in this real setting and compared to similar systems.

The Impact of ICTs on Lecturer and Student Interaction in University Education Processes

Interaction is a basic element in any educational process, and it is something that needs to be reconsidered in the light of technology. In order to examine the methodological changes that ICTs bring to teaching from an interaction perspective, a study was carried out at the University of Lleida to observe interaction processes in various face-to-face, blended learning and e-learning subjects. The methodological design was based on three data collection techniques: documentary analysis of subject curricula, lecturer and student questionnaires, and lecturer interviews. The data showed that, as the online component of subjects increased, the lecturers and students used more technological tools to communicate (e-mail, forums, chats, social networks, etc.). Furthermore, we found that the lecturers and students basically communicated for academic purposes. While they hardly ever communicated for personal reasons (guidance, support, etc.), they claimed that closer contact with a non-academic focus would be preferable. We also observed that the students’ work was more individual in e-learning subjects. Although there is still a considerable way to go in ICT-mediated lecturer-student interaction, both the lecturers and students recognise the potential of such technologies, even though they still do not use them as they feel they should.

Teaching how to learn with a wiki in Primary Education: what classroom interaction can tell us

Understanding how wikis are used to support collaborative learning is an important concern for researchers and teachers. Adopting a discourse analytic approach, this paper attempts to understand the teaching processes when a wiki is embedded in a science project in primary education to foster collaborative learning. Through studying interaction between the teacher and students, our findings identify ways in which the teacher prompts collaborative learning but also shed light on the difficulties for the teacher in supporting student collective collaboration. It is argued that technological wiki features supporting collaborative learning can only be realized if teacher talk and pedagogy are aligned with the characteristics of wiki collaborative work: the freedom of students to organize and participate by themselves, creating dialogic space and promoting student participation. We argue that a dialogic approach for examining interaction can be used to help to design a more effective pedagogic approach in the use of wikis in education, to shift into Web 2.0 learning paradigm and to equip learners with the competences they need to participate in knowledge co-construction.