Polytechnic University of Valencia

About: Polytechnic University of Valencia is a education organization based out in Valencia, Spain. It is known for research contribution in the topics: Catalysis & Population. The organization has 16282 authors who have published 40162 publications receiving 850234 citations.

Evolutionary Diversification in Polyamine Biosynthesis

Abstract: Polyamine biosynthesis is an ancient metabolic pathway present in all organisms. Aminopropyltransferases are key enzymes that mediate the synthesis of spermidine, spermine, and thermospermine. The relatively high sequence similarity between aminopropyltransferases and their similarity with putrescine N-methyltransferases (PMT) raises the question of whether they share a common ancestor or have evolved by convergence. Here we show that aminopropyltransferases and PMT are phylogenetically interconnected, and the different activities have been generated by unusually frequent events of diversification of existing functions. Although all spermidine synthases (SPDSs) derive from a common ancestor preceding the separation between prokaryotes and eukaryotes, they have been the origin of a variety of new activities. Among those, spermine synthases (SPMSs) represent a novelty independently arisen at least 3 times, in animals, fungi, and plants. The most parsimonious mechanism would involve the duplication and change of function of preexisting SPDS genes in each phylum. Although spermine is not essential for life, the repeated invention of SPMS and its conservation strongly argues for an evolutionary advantage derived from its presence. Moreover, the appearance of thermospermine synthase (tSPMS) in several genera of Archaea and Bacteria was accompanied by a loss of SPDS, suggesting that the new activity originated as a change of function of this enzyme. Surprisingly, tSPMS was later acquired by plants at an early stage of evolution by horizontal gene transfer and has proven to be essential for vascular development in tracheophytes. Finally, the synthesis of nicotine and tropane alkaloids in Solanales was favored by the origination of a new activity, PMT, as a duplication and change of function from SPDS.

Chemoselective Hydrogenation Catalysts: Pt on Mesostructured CeO2 Nanoparticles Embedded within Ultrathin Layers of SiO2 Binder

Abstract: Pt on mesostructured CeO2 nanoparticles embedded within ultrathin layers of highly structured SiO2 binder shows highest activity reported with 80% selectivity for the chemoselective hydrogenation of crotonaldehyde. Characterization by transmission electron microscopy (TEM), CO adsorption, and X-ray photoelectron spectroscopy (XPS) show the presence of small Pt metal particles, preferentially located on CeO2 (70%) together with the formation of Pt−CeO2-x sites at the interface between Pt and CeO2 (4 nm) nanoparticles. These sites are able to polarize the carbonyl group and facilitate the selective hydrogenation of this with respect to the double bond.

Simulation/gaming and the acquisition of communicative competence in another language

Abstract: For more than three decades, researchers and practitioners in the field of English as a foreign language have faced the issue of communicative competence as a goal in language acquisition and how to reach this goal. In this article, the authors address the issue from the point of view of a theoretical and practical meshing of simulation and gaming methodology with theories of foreign language acquisition, including task-based learning, interaction, and comprehensible input, showing how simulation and gaming can be used in those phases of language acquisition in which formal instruction has proved less ineffectual. The objective of this article is to describe the close relationship between the acquisition of foreign language competence and its components and experiential learning through simulation and gaming, with specific reference to two experiments in this area.