Top-Down Mass Analysis of Protein Tyrosine Nitration: Comparison of Electron Capture Dissociation with “Slow-Heating” Tandem Mass Spectrometry Methods

Tyrosine nitration in proteins is an important post-translational modification (PTM) linked to various pathological conditions. When multiple potential sites of nitration exist, tandem mass spectrometry (MS/MS) methods provide unique tools to locate the nitro-tyrosine(s) precisely. Electron capture dissociation (ECD) is a powerful MS/MS method, different in its mechanisms to the “slow-heating” threshold fragmentation methods, such as collision-induced dissociation (CID) and infrared multiphoton dissociation (IRMPD). Generally, ECD provides more homogeneous cleavage of the protein backbone and preserves labile PTMs. However recent studies in our laboratory demonstrated that ECD of doubly charged nitrated peptides is inhibited by the large electron affinity of the nitro group, while CID efficiency remains unaffected by nitration. Here, we have investigated the efficiency of ECD versus CID and IRMPD for top-down MS/MS analysis of multiply charged intact nitrated protein ions of myoglobin, lysozyme, and cytochrome c in a commercial Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. CID and IRMPD produced more cleavages in the vicinity of the sites of nitration than ECD. However the total number of ECD fragments was greater than those from CID or IRMPD, and many ECD fragments contained the site(s) of nitration. We conclude that ECD can be used in the top-down analysis of nitrated proteins, but precise localization of the sites of nitration may require either of the “slow-heating” methods

Studies on post-synthetic treatments of micro- and mesoporous zeolites:Impact on their physicochemical and catalytic properties

Zeolites have a very wide application range, including the use as catalysts. Actually, zeolites constitute a large portion of the solid catalysts used to date in industry. The major challenge nowadays is the fine-tuning of these materials to a specific application, either by direct synthesis or by a combination with post-synthesis treatments. A well-known post synthesis treatment method is calcination, typically used to remove the organic template and/or to introduce Brønsted acid sites in the zeolite framework. However, calcination has some major drawbacks, such as a (partly) collapse of the structure and a reduction of the OH groups on the surface. In this thesis, the use of milder post-treatment techniques is described, with an emphasis on Fenton detemplation. The suitability of this methodology was determined for a number of relevant micro- and meso-porous zeolites and quantitative template removal was observed in most cases. Relevant material properties were determined and it was shown that the structure of the zeolite after the mild detemplation procedure resembles that of the zeolite after synthesis. The catalytic cracking of low-density polyethylene (LDPE) was used as model reaction to test performance of the various detemplated zeolites. It was shown that zeolites prepared using the mild Fenton approach were more active than those prepared using the conventional calcination technique

Preparation of Poly(Vinyl) Alcohol/Chitosan Hybrid Membranes Doped with Graphene Nanosheets

The development of ion exchange membrane technology has allowed its introduction in many industrial sectors, such as electrodialysis and electrolysis. Nowadays, membranes are the crucial element in electrochemical energy conversion and storage devices. This work is aimed at examining new eco-friendly membranes materials to improve structural, mechanical, electrical and barrier properties. A simple and ecological synthesis of alkaline anion exchange membranes based on a mixed matrix membrane of chitosan (CS) and poly(vinyl) alcohol (PVA) – CS:PVA polymeric matrix – was developed by using a 50:50 wt. % ratio. The CS:PVA matrix was modified with variable loadings of graphene pristine sheets (GPH) ranging between 0,5 and 4.0 wt. %. The physico-chemical characterization of each of the membranes prepared was carried out in order to examine the topology, structure, thermal stability, surface chemistry, and water content (WC), as well as the ionic conductivity by using electrochemical impedance spectroscopy (EIS). Results revealed that the incorporation of graphene (GPH) into the CS:PVA polymeric matrix leads to the improvement of the thermal stability, and the ionic conductivity of the pristine polymeric matrix. The loading of 1.0 wt. % of GPH into CS:PVA was optimal in terms of specific ionic conductivity that is related to surface chemistry of the membrane, WC, and slight roughness of the membrane topology. The presence of GPH only provided a slight loss of crystallinity of the memebrane compared to the unmodified CS:PVA membrane, which also resulted in the reduction of water content with moderately GPH loadings. With regard to the ionic conductivity, an almost twofold increase was obtained compared to the pure CS:PVA for an optimal loading of 1.0 wt. %.The authors thank the Ministerio de Economía y Competitividad for its financial support (CTQ2013-48280-C3-3-R). Also, Jesús Iniesta gives thanks to Relaciones Internacionales for the PPI grant suppoted by the University of Alicante, Spain

Use of Chitosan as Copper Binder in the Continuous Electrochemical Reduction of CO2 to Ethylene in Alkaline Medium

This work explores the potential of novel renewable materials in electrode fabrication for the electrochemical conversion of carbon dioxide (CO2) to ethylene in alkaline media. In this regard, the use of the renewable chitosan (CS) biopolymer as ion-exchange binder of the copper (Cu) electrocatalyst nanoparticles (NPs) is compared with commercial anion-exchange binders Sustainion and Fumion on the fabrication of gas diffusion electrodes (GDEs) for the electrochemical reduction of carbon dioxide (CO2R) in an alkaline medium. They were tested in membrane electrode assemblies (MEAs), where selectivity to ethylene (C2H4) increased when using the Cu:CS GDE compared to the Cu:Sustainion and Cu:Fumion GDEs, respectively, with a Faradaic efficiency (FE) of 93.7% at 10 mA cm−2 and a cell potential of −1.9 V, with a C2H4 production rate of 420 µmol m−2 s−1 for the Cu:CS GDE. Upon increasing current density to 90 mA cm−2, however, the production rate of the Cu:CS GDE rose to 509 µmol/m2s but the FE dropped to 69% due to increasing hydrogen evolution reaction (HER) competition. The control of mass transport limitations by tuning up the membrane overlayer properties in membrane coated electrodes (MCE) prepared by coating a CS-based membrane over the Cu:CS GDE enhanced its selectivity to C2H4 to a FE of 98% at 10 mA cm−2 with negligible competing HER. The concentration of carbon monoxide was below the experimental detection limit irrespective of the current density, with no CO2 crossover to the anodic compartment. This study suggests there may be potential in sustainable alernatives to fossil-based or perfluorinated materials in ion-exchange membrane and electrode fabrication, which constitute a step forward towards decarbonization in the circular economy perspective.This research was funded by the Spanish Ministry for Science and Innovation, grant numbers PID2019-108136RB-C31, PID2019-108136RB-C32, PID2020-112845RB-I00 and EIN2020-112319. A.M.M. also acknowledges the Ministry for the Early Stage researcher contract (FPI grant no. BES-2017-080795)

Sustainable development goals and education for sustainable development: applications to the teaching of the Chemical Kinetics subject of the Degree in Chemistry

El objetivo de este artículo es presentar una propuesta didáctica enmarcada en la educación para el desarrollo sostenible (EDS) que incorpore los Objetivos de Desarrollo Sostenible (ODS) para permitir al alumnado profundizar en temas globales en la asignatura Cinética Química (CQ) en la enseñanza universitaria. Se describirán las actividades de CQ y se establecerán las relaciones entre los ODS y la adquisición de las competencias y los contenidos, prestando especial atención a la sostenibilidad como tema transversal. Se presentará el análisis de una encuesta anónima con el fin de obtener datos cuantitativos y así valorar la eficacia de las actividades enmarcadas en la EDS que el alumnado realiza en la asignatura. La encuesta revela que el alumnado ha tomado conciencia de que además de adquirir conocimientos, profundiza en los ODS y en competencias sociales útiles tanto para su vida laboral como personal.The purpose of this article is to present a didactic proposal framed in Education for Sustainable Development (ESD) that incorporates the Sustainable Development Goals (SDGs) to allow students deepen on global issues in the Chemical Kinetics (CK) subject in higher education. The activities of CK will be described and the relationships between the SDGs and the acquisition of competences and contents will be established, with particular attention to sustainability as a cross-cutting theme. The analysis of an anonymous survey will be presented in order to obtain quantitative data and thus to value the effectiveness of the activities framed in the ESD that students carry out in the subject. The survey reveals that students have become aware that in addition to acquiring knowledge, they also deepen on the SDGs, and on social competences that will be useful for both their lives and their professional careers

Nanoporous carbon/WO3 anodes for an enhanced water photooxidation

This work provides new insights in the field of applied photoelectro chemistry based on the use of nanoporous carbons as additives to tungsten oxide for the photooxidation of water under potential bias. Using a nanoporous carbon of low surface functionalization as additive to WO3 we have shown the dependence of the photochemical oxidation of water with the wavelength of the irradiation source. Photoelectrochemical responses obtained under monochromatic illumination show a significant increase in the incident photon-to-current conversion efficiency (IPCE) values for electrodes featuring up to 20 wt% carbon additive. Photoelectrochemical transient responses also show a sharp potential dependence, suggesting that the performance of the electrodes is strongly influenced by the carrier mobility and recombination losses. Despite the modest IPCE values of the W/NC electrodes (due to high bulk recombination and poor electron transport properties of the electrodes), our data shows that the incorporation of an optimal amount of nanoporous carbon additive to WO3 can enhance the carrier mobility of the semiconductor, without promoting additional recombination pathways or shadowing of the photoactive oxide.COA thanks the financial support of the European Research Council through a Consolidator Grant (ERC-CoG-648161-PHOROSOL) and the Spanish MINECO (grants CTM2014/56770-R, CTQ2013-48280-C3-3-R). VC and DJF kindly thank the UK Catalysis Hub for resources and support provided via the membership of the UK Catalysis Hub Consortium and funded by EPSRC (grants EP/K014706/1, EP/K014668/1, EP/K014854/1, EP/K014714/1 and EP/M013219/1). AGB thanks her PhD fellowship (BES-2012-060410) and VC thanks the UK National Academy and the Royal Society by the support though the Newton International Fellows program

On the performance of carbon-based screen-printed electrodes for (in)organic hydroperoxides sensing in rainwater

Hydroperoxides play important roles in atmospheric chemical processes since they act as strong oxidants. This paper details with the modification, characterization and performance of different carbon-based screen-printed electrodes to develop a sensor that allows to analyze organic and inorganic hydroperoxides in atmospheric samples. Commercial electrodes made up of graphite, graphene, carbon nanotubes and graphene oxide were electrochemically activated and subsequently modified by layer-by-layer method with a conducting polymer of azure-A and electrodeposited platinum nanoparticles. Characterization of modified electrodes was performed by FE-SEM, XPS, Raman spectroscopy, cyclic voltammetry, and impedance spectroscopy. Even though all modified carbonaceous substrates enabled the development of competitive electrochemical sensors for (in)organic hydroperoxides detection, carbon nanotubes underlying substrate exhibited the best performances in terms of sensitivity, stability, limit of detection and linear range. This amperometric sensor displayed linear responses to hydroperoxides over 0.081–450 μM with detection limits in the range of 24–558 nM and sensitivity values among 0.0628±1.6E-4 and 0.0112±0.71E-4 μA/μM for the different hydroperoxides herein studied. The developed electrochemical sensor was successfully applied to the analysis of (in)organic hydroperoxides in rainwater samples. Measurements in rainwater were performed in a city located in the East of Spain and collected at two different sites (downtown and suburban area) on two different dates (July and November 2020). The presented results demonstrated high sensitivity and selectivity for the detection of hydroperoxides among a plethora of substances naturally present in rainwater.This research was supported by the Spanish Ministry of Science, Innovation and Universities (MICINN, https://www.ciencia.gob.es/) with grants PID2019-106468RB-I00 and PID2019-108136RB-C32, the Junta de Comunidades de Castilla-La Mancha with grant SBPLY/17/180501/000276/2, and the UCLM groups research grants 2020-GRIN-28857 and 2020-GRIN-28771, all of them cofounded with FEDER funds, EU

Carbon materials for the electrooxidation of nucleobases, nucleosides and nucleotides toward cytosine methylation detection: a review

Improved analytical methods for the determination of the degree of methylation of DNA are of vital relevance, as they may enable the detection of certain diseases, such as carcinomas and infertility, in the early stages of development. Among the analytical methods for the detection and quantification of epigenetic modifications in DNA, electroanalytical platforms are emerging as potential feasible tools for clinical purposes. This review describes the fundamentals of the electrochemical responses of nucleobases, nucleosides, nucleotides and DNA in general from the pioneering studies at mercury electrodes to the most recent studies during the last two decades. Concerning these latter studies, we will exclusively focus on carbonaceous electrodes such as carbon, graphite, glassy carbon, boron-doped diamond, carbon nanofibers, carbon nanotubes and graphene. This review will also provide an overview of the feasibility of the development of electrochemical sensors for the simultaneous determination and quantification of naturally occurring DNA bases and nucleotides as well as the methylation of cytosine in DNA using carbon materials.The authors give thanks to the University of Alicante for funding and collaboration in this review. This work has also been financially supported by the MICINN-FEDER (Spain) through the projects CTQ2013-48280-C3-3 R and CTQ2013-44083-P

[4+2]-Cycloaddition of sterically hindered thiophene S-oxides to alkenes and SO extrusion reactions of the cycloadducts

Cycloaddition reactions of 2,5-di-tert-butylthiophene S-oxide and 2,3,4,5-tetrakis(p-tolyl)thiophene S-oxide with alkenes are described. The reactivity of 2,5-di-tert-butylthiophene S-oxide as diene in Diels–Alder reactions is compared with 2,5-di-tert-butylthiophene S,S-dioxide. The thermal and photochemical SO extrusion reactions of the cycloadducts under formation of highly substitutedaromatic compounds are exemplified.This project was supported in part by ESPRC (in UK) and J. Iniesta thanks the ESPRC for funding of a stay at Kyushu University, Fukuoka, Japan