Comunidad de Aprendizaje Práctico Universitario (CAPU) para la realización de Trabajos Fin de Grado en el Departamento de Derecho Internacional

Memoria del Proyecto de Innovación Docente UCM nº 144/2022, que tiene por objeto una metodología para la realización del Trabajo de Fin de Grado de las asignaturas de Derecho Internacional Privado y Derecho Internacional Público, mediante una serie de preguntas elaboradas por el grupo de profesores sobre un conflicto o controversia internacional, de tal forma que el tema y las preguntas a responder por los alumnos esté preestablecido.Depto. de Derecho Internacional, Eclesiástico y Filosofía del DerechoFac. de DerechoFALSEsubmitte

Aplicaciones de los isótopos estables enriquecidos y la deconvolución de perfiles isotópicos en ICP-MS

Tesis doctoral por el sistema de Compendio de PublicacionesLa Espectrometría de Masas con fuente de acoplamiento inductivo (ICP-MS) se puede considerar como la técnica de referencia en análisis elemental debido a su alta sensibilidad como a su carácter multielemental. En los últimos años, los equipos ICP-MS han ganado una enorme popularidad y ya están presentes en la mayoría de los laboratorios públicos o privados españoles que realizan análisis de trazas metálicas. La mayoría de las determinaciones analíticas se realizan mediante un calibrado metodológico con patrones internos por lo que la información isotópica que proporcionan los equipos ICP-MS se utiliza únicamente para comprobar la ausencia de interferencias espectrales por la comparación de perfiles isotópicos en las muestras respecto de un patrón teórico. Hasta hace poco tiempo el uso de la dilución isotópica en análisis elemental estaba restringido a su aplicación a la certificación de materiales de referencia o la asignación de valores certificados en ejercicios de intercomparación. Hoy en día no existe ninguna limitación, ni teórica ni practica, que impida la utilización generalizada de la dilución isotópica en análisis de rutina. En la presente tesis doctoral se han desarrollado metodologías analíticas, basadas en el empleo de isótopos estables enriquecidos, que pueden ser utilizadas en conjunción con el ICP-MS en análisis de rutina. Estas metodologías han sido validadas a través de la participación en ejercicios de intercomparación y han sido aplicadas en la organización a nivel nacional de un ejercicio de intercompación para la determinación de metales traza en aguas. Además, se han desarrollado metodologías de cálculo alternativo, basadas en la regresión lineal múltiple, que simplifican la aplicación de la dilución isotópica en análisis de rutina corrigiendo errores sistemáticos en el análisis por dilución isotópica. Estas metodologías han sido aplicadas en estudios metabólicos como en otros campos como el nuclear y el de marcaje de productos y organismos. La regresión lineal múltiple también ha sido aplicada a la medida directa de abundancias y relaciones isotópicas cuando lo que se pretende conocer son las variaciones naturales por efectos de decaimiento radioactivo o procesos de fraccionamiento isotópico. Estas metodologías han sido aplicadas al estudio de las relaciones isotópicas de neodimio y samario y al fraccionamiento isotópico del mercurio

Iron uptake and distribution in sugar beet plants treated with racemic and meso Fe(III)-o,oEDDHA isomers

1 .pdf copia del póster original presentado por los autores en el Simposio Internacional. Se acompaña de 1 .pdf copia del resumen oficial.The synthetic ferric chelate based on the molecule ethylenediamine-N,N’-bis(hydroxyphenylacetic)acid, commonly named as Fe(III)-o,oEDDHA, is one of the most efficient fertilizers used to correct Fe deficiency in crops growing in calcareous soils. Iron(III)-o,oEDDHA has two diastereoisomers, the meso form and the racemic mixture, which are present in approximately equal amounts in commercial Fe-chelate fertilizer formulations. In previous studies, evidence was presented that Strategy I plants (tomato, pepper [1], bean [2, 3] and cucumber [4]) take up Fe preferentially from the meso chelate form when compared to the racemic one. The aim of the present work was to determine the differences in Fe uptake and distribution inside the plant between both Fe(III)-o,oEDDHA isomers, using the Strategy I species sugar beet, stable Fe isotopes (54Fe and 57Fe) and inductively coupled plasma-mass spectrometry (ICP-MS). Both Fe(III)-o,oEDDHA isomers were separated by selective Mg precipitation, then Fe was removed and the resulting o,oEDDHA acid isomers were chelated with 54Fe or 57Fe. Iron-deficient sugar beet plants were treated for 24 hours with i) 30 µM racemic 57Fe(III)-o,oEDDHA : 30 µM meso 54Fe(III)-o,oEDDHA or ii) 30 µM racemic 54Fe(III)-o,oEDDHA : 30 µM meso 57Fe(III)-o,oEDDHA. Roots, xylem sap, old and young leaves were sampled, and the 56Fe, 54Fe and 57Fe contents in all plant materials and nutrient solutions were determined by isotope dilution analysis and ICP-MS. Plants took up Fe preferentially from the meso Fe(III)-o,oEDDHA isomer, independently of the Fe stable isotope used. However, the distribution of the Fe supplied by both isomers inside the plant was different, since the Fe isotope supplied by the meso isomer accumulated preferentially in roots, whereas plant shoot materials (xylem and leaves) had similar contents of the Fe isotopes provided by both isomers. Therefore, it can be concluded that both isomers were equally effective in allocating Fe in aerial plant parts, whereas the meso isomer was more effective in allocating Fe in roots.This study was supported by the Spanish Ministry of Science and Education (projects AGL2006-1416 and AGL2007-61948, co-financed with FEDER), the European Commission (EU 6th Framework Integrated Project ISAFRUIT), and the Aragón Government (group A03).Peer reviewe

Identification of a Tri-Iron(III), Tri-Citrate Complex in the Xylem Sap of Iron-Deficient Tomato Resupplied with Iron: New Insights into Plant Iron Long-Distance Transport

12 páginas, 5 figuras, 2 tablas.The identification of Fe transport forms in plant xylem sap is crucial to the understanding of long-distance Fe transport processes in plants. Previous studies have proposed that Fe may be transported as an Fe–citrate complex in plant xylem sap, but such a complex has never been detected. In this study we report the first direct and unequivocal identification of a natural Fe complex in plant xylem sap. A tri-Fe(III), tri-citrate complex (Fe3Cit3) was found in the xylem sap of Fe-deficient tomato (Solanum lycopersicum Mill. cv. ‘Tres Cantos’) resupplied with Fe, by using an integrated mass spectrometry approach based on exact molecular mass, isotopic signature and Fe determination and retention time. This complex has been modeled as having an oxo-bridged tri-Fe core. A second complex, a di-Fe(III), di-citrate complex was also detected in Fe–citrate standards along with Fe3Cit3, with the allocation of Fe between the two complexes depending on the Fe to citrate ratio. These results provide evidence for Fe–citrate complex xylem transport in plants. The consequences for the role of Fe to citrate ratio in long-distance transport of Fe in xylem are also discussed.This work was supported by the Spanish Ministry of Science and Innovation (grant numbers AGL2006-1416, AGL2007-61948 and CTQ2006-05722, co-financed with FEDER); the European Commission (Thematic Priority 5—Food Quality and Safety, 6th Framework RTD Programme, grant number FP6-FOOD-CT-2006-016279) and the Aragón Government (groups A03 and E39). Acquisition of the HPLC–TOFMS apparatus was cofinanced with FEDER. R.R.-A., J.G.-M.-S., I.O. and J.A.R.-C. were supported by FPI-MICINN, FICYT-MICINN, CONAID-DGA and FPU-MICINN grants, respectively.Peer reviewe

Enriched stable isotopes and isotope pattern deconvolution for quantitative speciation of endogenous and exogenous selenium in rat urine by HPLC-ICP-MS

Interest in selenium metabolism and its role in health and disease continue to stimulate a lot of bioanalytical research. The use of enriched stable isotopes of Se and isotope pattern deconvolution (IPD) with an ICP-MS in lactating rats is approached here for total selenium distribution studies. A mathematical tool has been developed to calculate supplemented and endogenous total Se contents in urine and faeces by ICP-MS. Also, quantification of endogenous (natural) and exogenous seleno-species by HPLC-ICP-MS has been worked out. The proposed IPD methodology, for total determinations and for quantitative speciation, was applied to reference materials to validate total selenium quantification in faeces and quantitative selenium speciation in urine samples. Selenium apparent absorption and retention and natural and exogenous selenium distribution in urine samples were calculated. Interesting quantitative information about selenium bio-transformations and final catabolism can be obtained from careful examination of the results observed, using such analytical tools, of the urinary endogenous and exogenous selenium metabolites in urine of rats and their kinetics throughout the two weeks of selenium supplementation

Using a dual-stable isotope tracer method to study the uptake, xylem transport and distribution of Fe and its chelating agent from stereoisomers of an Fe(III)-chelate used as fertilizer in Fe-deficient Strategy I plants

12 Pags., 1 Tabl., 8 Figs.A dual-stable isotope tracer experiment was carried out with Fe-deficient sugar beet plants grown hydroponically and resupplied with differentially Fe labeled racemic and meso Fe(III)-chelates of the ethylendiamine di(o-hydroxyphenylacetic) acid (o,oEDDHA). No short-term Fe isotope exchange reactions occurred in the nutrient solution and plants did not discriminate between 54Fe and 57Fe. After 3–6 h, stable Fe isotopes, chelating agents and chelates were analyzed in roots, xylem sap and leaves by ICP-MS and HPLC-ESI/TOFMS. Ferric chelate reductase rates, xylem transport and total uptake were 2-fold higher with the meso isomer than with the racemic one. Both chelating agent isomers were incorporated and distributed by plants at similar rates, in amounts one order of magnitude lower than those of Fe. After 6 h of Fe resupply, most of the Fe acquired was localized in roots, whereas most of the chelating agent was in leaves. In a separate experiment, Fe-deficient sugar beet and tomato plants were treated with different concentrations of Fe(III)-o,oEDDHA (with a meso/racemic ratio of 1). The xylem sap Fe concentration at 24 h was unaffected by the chelate concentration, with xylem Fe(III)-o,oEDDHA accounting for 1–18% of total Fe and xylem meso/racemic ratio close to 1. Although most of the Fe coming from Fe(III)-o,oEDDHA was taken up through a reductive dissociative mechanism, a small part of the Fe may be taken up via non-dissociative mechanisms.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) (projects AGL2007-61948 and AGL2009-09018, co-financed with FEDER), the Commission of European Communities (ISAFRUIT Project, Thematic Priority 5-Food Quality and Safety, of the 6th Framework Programme of RTD; Contract No. FP6-FOOD-CT-2006- 016279), the trilateral Project Hot Iron (ERA-NET Plant Genome Research KKBE; MICINN EUI2008-03618) and the Arago´ n Government (Group A03). IO was supported by a CONAID-DGA predoctoral fellowship and a CAI-Europa grant.Peer reviewe