Phospholipases a2 from Viperidae snakes: Differences in membranotropic activity between enzymatically active toxin and its inactive isoforms

artículo -- Universidad de Costa Rica, Instituto de Investigaciones Clodomiro Picado. 2015. Este documento es privado debido a limitaciones de derecho de autor.We describe the interaction of various phospholipases A2 (PLA2) from snake venoms of the family Viperidae (Macrovipera lebetina obtusa, Vipera ursinii renardi, Bothrops asper) with giant unilamellar vesicles (GUVs) composed of natural brain phospholipids mixture, visualized through fluorescence microscopy. The membrane fluorescent probes 8-anilino-1-naphthalenesulfonicacid (ANS), LAUDRAN and PRODAN were used to assess the state of the membrane and specifically mark the lipid packing and membrane fluidity. Our results have shown that the three PLA2s which contain either of aspartic acid, serine, or lysine residues at position 49 in the catalytic center, have different effects on the vesicles. The PLA2 with aspartic acid at this position causes the oval deformation of the vesicles, while serine and lysine-containing enzymes lead to an appreciable increase of fluorescence intensity in the vesicles membrane, wherein the shape and dimensions of GUVs have not changed, but in this case GUV aggregation occurs. LAURDAN and PRODAN detect the extent of water penetration into the bilayer surface. We calculated generalized polarization function (GP), showing that for all cases (D49 PLA2, S49 PLA2 and K49 PLA2) both LAUDRAN and PRODAN GP values decrease. A higher LAURDAN GP is indicative of low water penetration in the lipid bilayer in case of K49 PLA2 compared with D49 PLA2, whereas the PRODAN mainly gives information when lipid is in liquid crystalline phase.Russian Foundation for Basic Research. Universidad de Costa Rica.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP

The Union and the Turkish recognition of the Armenian “genocide” in the broader framework of the EU external action: a tale of possibilities yet to be explored

Throughout decades of partnership, the European Union (EU) has never opened a dialogue with Turkey regarding its refusal to recognise the 1915-1916 “genocide.” This paper evaluates this lack of action against a multilevel legal background: in bilateral relations with Turkey, the European Economic Community lacked powers in the field of foreign policy until the Treaty of Maastricht, although an association agreement was operational; since 1993, a full-fledged external-action machinery became available; in multilateral relations, the EU developed a policy vis-à-vis its Eastern neighbourhood, which evolved over the years. As remarkable as it may be as the only act produced outside the framework of Turkey’s accession process, the European Parliament’s resolution on the “genocide” centenary also constitutes a missed opportunity. Despite the current difficult stage of relations between Turkey and the EU, some tools towards a possible solution are still available