The Ionic selectivity of large protein ion channels

Els canals iònics de gran amplada i de conductància alta exerceixen una funció molt important en el cicle de vida de les cèl· lules. Permeten l'intercanvi de soluts neutres i carregats a través de la membrana cel·lular i regulen l'aportació de nutrients i la sortida de deixalles. Per a realitzar aquesta funció, els canals han de discriminar entre diferents espècies iòniques. Els canals mesoscòpics permeten el transport multiiònic passiu i generalment presenten una selectivitat moderada respecte a ions positius i negatius. Aquí revisem les metodologies més usades per a estimar quantitativament la selectivitat iònica. Entre elles, la mesura del potencial elèctric necessari per a anul·lar el corrent elèctric a través del canal en presència d'un gradient de concentració, cosa que es coneix com a potencial de corrent zero. Assenyalem els factors clau que cal tenir en compte per a una interpretació física correcta d'aquests experiments d'electrofisiologia.Large, highly conductive ion channels have a major functional role in the cell life cycle. They allow the exchange of charged and neutral solutes across the cell membrane envelope and regulate the influx of nutrients and the extrusion of waste products. To perform this function, channels must discriminate between different ionic species. Mesoscopic channels allow multiionic, passive transport and are usually moderately selective toward positive or negative ions. Here we review one of the most common approaches used for the quantitative estimation of channel selectivity: the measurement of the potential needed to get zero current across a channel in the presence of an electrolyte concentration gradient, also known as Reversal Potential. We highlight several key points that need to be addressed for a correct physical interpretation of these experiments in electrophysiology

Plomo metálico en yacimientos de la I Edad del Hierro en la Provincia de Castellón: Explotación de recursos mineros y circulación del metal

Las investigaciones que estamos realizando en yacimientos de la I Edad del Hierro en la provincia de Castellón nos han permitido estudiar algunos de los primeros objetos de plomo caracterizando su composición mediante ED-XRFy ICP-MS. También se ha realizado un trabajo de localización de minas de plomo en la provincia, analizando las muestras recogidas en ellas para determinar su potencial uso para obtener plomo metálico o para extracción de plata. Finalmente tanto del material arqueológico como del geológico se han realizado análisis de isótopos de plomo con técnicas de alta precisión (TIMS o MC-ICP-MS) necesarias para conseguir una información comparable y minimizar los márgenes de error y de interpretación en la asignación a campos isotópicos de base geológica. Con estos análisis se pretende confirmar o rechazar el uso de los recursos provinciales de plomo durante este periodo histórico.HAR2010-21105-C02-02Peer reviewe

Electrostatics Explains the Shift in VDAC Gating with Salt Activity Gradient

AbstractWe have analyzed voltage-dependent anion-selective channel (VDAC) gating on the assumption that the states occupied by the channel are determined mainly by their electrostatic energy. The voltage dependence of VDAC gating both in the presence and in the absence of a salt activity gradient was explained just by invoking electrostatic interactions. A model describing this energy in the main VDAC states has been developed. On the basis of the model, we have considered how external factors cause the redistribution of the channels among their conformational states. We propose that there is a difference in the electrostatic interaction between the voltage sensor and fixed charge within the channel when the former is located in the cis side of membrane as opposed to the trans. This could be the main cause of the shift in the probability curve. The theory describes satisfactorily the experimental data (Zizi et al., Biophys. J. 1998. 75:704–713) and explains some peculiarities of VDAC gating. The asymmetry of the probability curve was related to the apparent location of the VDAC voltage sensor in the open state. By analyzing published experimental data, we concluded that this apparent location is influenced by the diffusion potential. Also discussed is the possibility that VDAC gating at high voltage may be better described by assuming that the mobile charge consists of two parts that have to overcome different energetic barriers in the channel-closing process

Estudio y control automático de la operación de extrusión de baldosas cerámicas

The ever-larger tile sizes demanded by the market, the higher quality requirements, and the increasingly similar installation to that of pressed products make it necessary to narrow the tolerance limits of final extruded tile size in order to maintain the product’s competitiveness. The results of this study show that, though mixing water has a great influence on drying shrinkage, it hardly affects extruded tile firing shrinkage. This indicates that control of the water added in the extrusion process is indispensable in order avoid variations in drying shrinkage and, thus, to assure good dimensional stability of the end produc

SARS-CoV-2 accessory protein 7b forms homotetramers in detergent

A global pandemic is underway caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The SARS-CoV-2 genome, like its predecessor SARS-CoV, contains open reading frames that encode accessory proteins involved in virus-host interactions active during infection and which likely contribute to pathogenesis. One of these accessory proteins is 7b, with only 44 (SARS-CoV) and 43 (SARS-CoV-2) residues. It has one predicted transmembrane domain fully conserved, which suggests a functional role, whereas most variability is contained in the predicted cytoplasmic C-terminus. In SARS-CoV, 7b protein is expressed in infected cells, and the transmembrane domain was necessary and sufficient for Golgi localization. Also, anti-p7b antibodies have been found in the sera of SARS-CoV convalescent patients. In the present study, we have investigated the hypothesis that SARS-2 7b protein forms oligomers with ion channel activity. We show that in both SARS viruses 7b is almost completely α-helical and has a single transmembrane domain. In SDS, 7b forms various oligomers, from monomers to tetramers, but only monomers when exposed to reductants. Combination of SDS gel electrophoresis and analytical ultracentrifugation (AUC) in both equilibrium and velocity modes suggests a dimer-tetramer equilibrium, but a monomer–dimer–tetramer equilibrium in the presence of reductant. This data suggests that although disulfide-linked dimers may be present, they are not essential to form tetramers. Inclusion of pentamers or higher oligomers in the SARS-2 7b model were detrimental to fit quality. Preliminary models of this association was generated with AlphaFold2, and two alternative models were exposed to a molecular dynamics simulation in presence of a model lipid membrane. However, neither of the two models provided any evident pathway for ions. To confirm this, SARS-2 p7b was studied using Planar Bilayer Electrophysiology. Addition of p7b to model membranes produced occasional membrane permeabilization, but this was not consistent with bona fide ion channels made of a tetrameric assembly of α-helices

The place of intertrochanteric osteotomy in the treatment of idiopathic necrosis of the head of the femur

The authors present their experience of the use of intertrochanteric osteotomy for the treatment of idiopathic necrosis of the head of the femur. The results obtained from 102 osteotomies performed on 81 patients with the disease are analysed. The mean follow-up is 4.2 years. The results show a statistically significant clinical improvement after operation. Patients presenting with Ficat and Arlet Stage II involvement fared much better than those with more severe changes. Better results were also seen in those with a necrosis angle of less than 200 degrees. No radiological improvement was seen although a high percentage showed no deterioration. The choice of treatment for the condition is discussed in the light of these results

On-line tools to improve the presentation skills of scientific results

[EN] In experimental sciences and engineering it is essential to communicate and present the results effectively. The authors have participated in several educational innovation projects since 2016, aimed at developing of materials to improve the communication skills of scientific results. An exhaustive and updated compilation of the international rules that constitute the basis for the writted and oral scientific presentations was carried out. The good teaching practices in these fields were also identified. The results of those previous projects have shown the need to incorporate web questionnaires and other interactive content into the educational program. These are adapted to the demands of the students and provide a training feeback. In this contribution, the new materials that are being developed within the innovation project UV-SFPIE_PID19-1096780, funded by the University of Valencia, are presented. They are devoted to facilitate the acquisition of communication skills of scientific results. In particular, these tools combine ICT self-learning environments with traditional classroom teaching (blended learning). The project methodology includes educational data mining aimed at identifying the most effective materials and activities to achieve its objectives. The aim of these mixed learning tools is to facilitate the acquisition by the students of the necessary skills of oral and written communication, improve their presentation skills and, consequently, also their employability as university graduates.This work has been supported by the University of Valencia through project SFPIE_PID19-1096780.Campos-Taberner, M.; Gilabert, M.; Manzanares, J.; Mafé, S.; Cervera, J.; García-Haro, F.; Martínez, B.... (2020). On-line tools to improve the presentation skills of scientific results. IATED. 4907-4910. https://doi.org/10.21125/inted.2020.1342S4907491