Rede de Infraestruturas de Apoio á Investigación e ao Desenvolvemento Tecnolóxico (RIAIDT)

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    Validation of the traditional calorespirometric procedure using external respirometry to quantify the calorespirometric ratio of soil microbial metabolism
    (Elsevier, 2025-04-04) Piñeiro Gómez, Verónica; Lestido Cardama, Yago; Pérez Cruzado, César; Barros Pena, Nieves; Universidade de Santiago de Compostela. Departamento de Produción Vexetal e Proxectos de Enxeñaría; Universidade de Santiago de Compostela. Departamento de Física Aplicada
    The calorespirometric ratio is a metabolic indicator that can be useful in soil science for understanding thermodynamics and the carbon use efficiency of soil microbial metabolism. Calculating calorespirometric ratios for soil microbial metabolism involves the development of calorespirometric procedures using calorimeters of the heat conduction type. The calorespirometric measurements for soil microbial metabolism are recent and their calculation requires sensitive calorimeters and accurate measurements. Their interpretation for soils has been developing during the last years, but accuracy of the methods involved in their calculation are still under question. This paper analyses the precision of the traditional calorespirometric method to yield these calorespirometric ratios by comparison with analysis of respiration measured in parallel using chromatography. Results indicated that the CO2 data obtained by chromatography and calorespirometry are significantly correlated with each other and with the heat rate of the soil microbial metabolism. The comparison of the CO2 data from both methods by the paired sample Wilcoxon signed rank test yielded no statistically significant differences. Nevertheless, small changes in the CO2 determinations, due to the method of measurement or to the reproducibility of these indices in the soil replicates, affected the experimental quantitative values of the calorespirometric ratios. Differences in the quantitative values were large enough in some of the samples to yield distinct interpretations of the results.
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    Thermal Transformation of Natural Schwertmannite in the Presence of Chromium
    (MDPI, 2022-06) Lázaro, Carlos; Antelo Cortizas, Juan Manuel; Carabante, Iván; Otero-Fariña, Alba; Vázquez Verdes, Pedro; Dacunha-Marinho, Bruno; Fiol López, Sarah; Universidade de Santiago de Compostela. Centro Interdisciplinar de Investigación en Tecnoloxías Ambientais (CRETUS); Universidade de Santiago de Compostela. Departamento de Edafoloxía e Química Agrícola; Universidade de Santiago de Compostela. Departamento de Química Física
    Schwertmannite is a metastable mineral playing a crucial role in the immobilization of metal(oid)s in acid mine drainage (AMD) systems. High temperatures associated with wildfires could lead to a sudden schwertmannite transformation, changing the mobility of metal(oid)s. The objective of the present study was to examine the thermal transformation from schwertmannite to hematite, and the subsequent effect on the chromium partitioning. The immobilization of arsenate after thermal transformation and its implications on chromium mobility was also evaluated. Natural schwertmannite, with increasing contents of chromium, was thermally treated between 200 to 800 °C. Transformation products were characterized by solid-phase techniques and selective chemical extractions. Results indicated a transformation to hematite at temperatures above 400 °C. The presence of chromium barely affected the temperature at which the transformation occurred, although partitioning of chromium in the mineral changed with temperature. As the temperature increased from 25 °C to 400 °C, chromium was less mobile and less outcompeted by arsenic adsorption, suggesting a larger contribution of inner-sphere complexes with increasing temperature. At temperatures above 600 °C, non-mobile forms strongly associated with neo-formed hematite were found. Finally, neo-formation of hematite led to a decrease in arsenic adsorption, implying a potentially enhanced arsenic mobility in AMD systems upon wildfires.
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    A multi-shot target-wheel assembly for high-repetition-rate, laser-driven proton acceleration
    (Cambridge University Press, 2024) Peñas, J.; Bembibre, A.; Cortina Gil, María Dolores; Martín, L.; Reija, A.; Ruiz, C.; Seimetz, M.; Alejo Alonso, Aaron José; Benlliure Anaya, José Fernando; Universidade de Santiago de Compostela. Departamento de Física de Partículas; Universidade de Santiago de Compostela. Instituto Galego de Física de Altas Enerxías (IGFAE)
    A multi-shot target assembly and automatic alignment procedure for laser–plasma proton acceleration at high repetition rate are introduced. The assembly is based on a multi-target rotating wheel capable of hosting more than 5000 targets, mounted on a 3D motorized stage to allow rapid replenishment and alignment of the target material between laser irradiations. The automatic alignment procedure consists of a detailed mapping of the impact positions at the target surface prior to the irradiation that ensures stable operation of the target, which alongside the purpose-built design of the target wheel, enables operation at rates up to 10 Hz. Stable and continuous laser-driven proton acceleration at 10 Hz is demonstrated, with observed cut-off energy stability about 15%.
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    Soil C dynamics after deforestation and subsequent conversion of arable cropland to grassland in humid temperate areas
    (Elsevier, 2023) Omil Ignacio, Beatriz; Piñeiro, Verónica; Barros Pena, Nieves; Souza Alonso, Pablo; Campo, Julio; Merino García, Agustín; Universidade de Santiago de Compostela. Departamento de Edafoloxía e Química Agrícola; Universidade de Santiago de Compostela. Departamento de Física Aplicada
    Land use and plant-soil management influence soil organic C stocks and soil properties. This study aimed to identify the main mechanisms by which these factors alter soil organic matter (SOM) dynamics and stocks. Changes in the organic C pools and biochemical quality in different OM compartments were assessed: a) after deforestation and intensive cultivation (SOM loss) and then, b) after the conversion of cropland to grassland (SOM replenishment) in a chronosequence of recovery (1–45 years). Topsoil samples were subjected to physical fractionation to assess the distribution of free particulate OM (POM) and mineral associated OM (MAOM). SOM quality was characterized by 13C NMR spectroscopy, thermal analysis (DSC/TG), and microbial activity was monitored by isothermal microcalorimetry. Deforestation and intensive cultivation led to the loss of 80 % of the C stored in the upper mineral soil (up to 30–35 cm). The POM was almost depleted, MAOM underwent significant losses (>40 %) and all OM compounds, including the aromatic C, were affected. The large and unexpected loss of MAOM can be attributed to the low specific surface soil area and also to the labile (biodegradable) nature of the OM in this fraction. After 45 years, conversion of cropland to grassland recovered 68 % of the C lost in the mineral soil (mainly as MAOM), at an annual rate of 1.25 Mg C ha−1. The present findings showed that the persistence of long-term OM depends on how strongly organic compounds are adsorbed onto mineral surfaces (i.e., the specific surface area) and the biochemical nature of OM compounds. Adequate plant-soil management favoured the replenishment of the MAOM under these experimental conditions, and this fraction was an active pool in terms of C storage and biochemical quality. This study served to test current theories about changes in soil C fractions due to land use changes and soil-plant management.
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    Pharmacological inactivation of the prion protein by targeting a folding intermediate
    (Springer Nature, 2021) Spagnolli, Giovanni; Massignan, Tania; Astolfi, Andrea; Biggi, Silvia; Rigoli, Marta; Brunelli, Paolo; Libergoli, Michela; Ianeselli, Alan; Orioli, Simone; Boldrini, Alberto; Terruzzi, Luca; Bonaldo, Valerio; Maietta, Giulia; López Lorenzo, Nuria; Fernández Flores, Leticia Camila; Bugallo Codeseira, Yaiza; Tosatto, Laura; Linsenmeier, Luise; Vignoli, Beatrice; Petris, Gianluca; Gasparotto, Dino; Pennuto, Maria; Guella, Graziano; Canossa, Marco; Altmeppen, Hermann C.; Lolli, Graziano; Biressi, Stefano; Martín Pastor, Manuel; Rodríguez Requena, Jesús; Mancini, Ines; Barreca, Maria L.; Faccioli, Pietro; Biasini, Emiliano; Universidade de Santiago de Compostela. Centro de Investigación en Medicina Molecular e Enfermidades Crónicas; Universidade de Santiago de Compostela. Departamento de Psiquiatría, Radioloxía, Saúde Pública, Enfermaría e Medicina
    Recent computational advancements in the simulation of biochemical processes allow investigating the mechanisms involved in protein regulation with realistic physics-based models, at an atomistic level of resolution. These techniques allowed us to design a drug discovery approach, named Pharmacological Protein Inactivation by Folding Intermediate Targeting (PPI-FIT), based on the rationale of negatively regulating protein levels by targeting folding intermediates. Here, PPI-FIT was tested for the first time on the cellular prion protein (PrP), a cell surface glycoprotein playing a key role in fatal and transmissible neurodegenerative pathologies known as prion diseases. We predicted the all-atom structure of an intermediate appearing along the folding pathway of PrP and identified four different small molecule ligands for this conformer, all capable of selectively lowering the load of the protein by promoting its degradation. Our data support the notion that the level of target proteins could be modulated by acting on their folding pathways, implying a previously unappreciated role for folding intermediates in the biological regulation of protein expression
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    Mechanism of interaction between hydroxypropyl cellulose and water in aqueous solutions: Importance of polymer chain length
    (Wiley, 2020) Martín Pastor, Manuel; Stoyanov, Edmont
    The utilization of hydroxypropyl cellulose (HPC) can be regarded as unexpected with regard to certain applications, such as being employed as a solubility enhancer for poorly soluble drugs and as a solubilizing agent for nano‐suspensions and amorphous solid dispersions. However, the best results were obtained for low‐molecular weight (Mw) HPC grades with a short‐chain structure. Therefore, in this study, seven grades of HPC with different polymer chain lengths (Mw) are analyzed in various aqueous solutions by a combination of 1H quantitative NMR spectroscopy, diffusion NMR spectroscopy, and water ligand observed via gradient spectroscopy; these investigations provide insights into the remarkable solubilizing property of HPC at the molecular and supramolecular levels. Furthermore, the hydration and the water residence time are found to be strongly dependent on the polymer chain length of HPC. The quantitative results obtained herein indicate that HPCs with shorter chain lengths retain smaller amounts of water around their hydrated molecules, as compared to their counterparts with longer chain lengths
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    Structure of the Receptor-Binding Carboxy-Terminal Domain of the Bacteriophage T5 L-Shaped Tail Fibre with and without Its Intra-Molecular Chaperone
    (MDPI, 2015) García Doval, Carmela; Castón, José R.; Luque, Daniel; Granell, Meritxell; Otero Casas, José Manuel; Llamas Saiz, Antonio Luis; Renouard, Madalena; Boulanger, Pascale; Raaij, Mark J. van; Universidade de Santiago de Compostela. Centro de Investigación en Química Biolóxica e Materiais Moleculares; Universidade de Santiago de Compostela. Rede de Infraestruturas de Apoio á Investigación e ao Desenvolvemento Tecnolóxico
    Bacteriophage T5, a Siphovirus belonging to the order Caudovirales, has a flexible, three-fold symmetric tail, to which three L-shaped fibres are attached. These fibres recognize oligo-mannose units on the bacterial cell surface prior to infection and are composed of homotrimers of the pb1 protein. Pb1 has 1396 amino acids, of which the carboxy-terminal 133 residues form a trimeric intra-molecular chaperone that is auto-proteolyzed after correct folding. The structure of a trimer of residues 970–1263 was determined by single anomalous dispersion phasing using incorporated selenomethionine residues and refined at 2.3 Å resolution using crystals grown from native, methionine-containing, protein. The protein inhibits phage infection by competition. The phage-distal receptor-binding domain resembles a bullet, with the walls formed by partially intertwined beta-sheets, conferring stability to the structure. The fold of the domain is novel and the topology unique to the pb1 structure. A site-directed mutant (Ser1264 to Ala), in which auto-proteolysis is impeded, was also produced, crystallized and its 2.5 Å structure solved by molecular replacement. The additional chaperone domain (residues 1263–1396) consists of a central trimeric alpha-helical coiled-coil flanked by a mixed alpha-beta domain. Three long beta-hairpin tentacles, one from each chaperone monomer, extend into long curved grooves of the bullet-shaped domain. The chaperone-containing mutant did not inhibit infection by competition