Biologically Relevant Small Radicals

Biologically relevant small radicals are at the focus of the working group 4 (WG4) of the COST Action CM0603 (Free Radicals in Chemical Biology, CHEMBIORADICAL). This article surveys the areas of research being undertaken by the partners in WG4. The character of the radicals is described together with experimental techniques utilized to follow their structure and reactivity. Specifically, C-, S-, N- and O-centered radicals of small size, and their interaction with different biomolecules are described. Processes at the molecular level exemplifying important biological signaling and damaging pathways are introduced

Holistic approach to chemical degradation of Nafion membranes in fuel cells

The state of health of polyfluorinated sulfonic-acid ionomer membranes (e.g. Nafion) in low-temperature proton exchange membrane fuel cells (LT-PEMFCs) is negatively influenced by degradation phenomena occurring during their operation. As a consequence, the performance and durability of the membrane are decreased. In this article, we focus on simulating and predicting chemical membrane degradation phenomena using a holistic zero-dimensional kinetic framework. The knowledge of chemical degradation mechanisms is widely spread. We have collected and evaluated an extensive set of chemical mechanisms to achieve a holistic approach. This yields a set of 23 coupled chemical equations, which provide the whole cause and effect chain of chemical degradation in LT-PEMFCs (based on the Fenton reaction between Fe [sup] 2+ and H [sub] 2O [sub] 2 via the attack of hydroxyl radicals on the membrane, loss of ionomer moieties and emission of fluoride). Our kinetic framework allows the reproduction of experimentally accessible data such as fluoride emission rates and concentrations of ionomer moieties (from both in situ and ex situ tests). We present an approach, which allows estimations of the membrane lifetime based on fluoride emission rates. In addition, we outline the demetallation of Fe-N-C catalysts as a source of additional harmful iron species, which accelerate chemical membrane degradation. To demonstrate the expandability and versatility of the kinetic framework, a set of five chemical equations describing the radical scavenging properties of cerium agents is coupled to the main framework and its influence on membrane degradation is analysed. An automated solving routine for the system of coupled chemical equations on the basis of the chemical kinetic simulation tool COPASI has been developed and is freely accessible online (http://ptc-pc-139.tugraz.at/ cgi-bin/Membrane_Degradation/)

Electrochemical fixation of nitrogen and its coupling with biomass valorization with a strongly adsorbing and defect optimized boron-carbon-nitrogen catalyst

The electrochemical conversion of low-cost precursors into high-value chemicals using renewably generated electricity is a promising approach to build up an environmental friendly energy cycle, including a storage element. The large-scale implementation of such process can however only be realized by the design of cost-effective electrocatalysts with high efficiency and highest stability. Here, we report the synthesis of N and B co-doped porous carbons. The constructed B-N motives combine abundant unpaired electrons and Frustrated Lewis pairs (FLPs). They result in desirable performance for electrochemical N2 reduction reaction (NRR) and electrooxidation of 5-hydroxymethylfurfural (HMF) in absence of any metal co-catalyst. A maximum Faradaic efficiency of 15.2% with a stable NH3 production rate of 21.3 µg h-1 mg-1 is obtained in NRR. Besides, 2,5-furandicarboxylic acid (FDCA) is firstly obtained by using non-metal-based electrocatalysts at a conversion of 71% and with yield of 57%. Gas adsorption experiments elucidate the relationship between the structure and the ability of the catalysts to activate the substrate molecules. This work opens up deep insights for the rational design of non-metal-based catalysts for potential electrocatalytic applications and the possible enhancement of their activity by the introduction of FLPs and point defects at grain boundaries

SPG11: Clinical and genetic features of seven Czech patients and literature review.

SPG11 is one of the most frequent autosomal recessively inherited types of hereditary spastic paraplegias (HSP or SPG). We describe the first seven patients from the Czech Republic with biallelic pathogenic variants in the SPG11. The typical HSP neurological findings are present in all the described patients in that the signs of a complicated phenotype develop slowly. The speed of disease progression, and the severity of gait impairment, was fast in all patients but the phenotype varied from patient to patient. Thin corpus callosum was not observed in two patients. Two Czech SPG11 patients had unusual late onset of disease and both were compound heterozygotes for the c.5381T>C variant. Therefore, we looked for a potential ralationship between the type of variant in the SPG11 gene and the age of disease onset. By reviewing all described SPG11 patients carrying at least one missense pathogenic variant in the SPG11 gene we did not found any relationship between the age of onset and the type of variant. Together twelve pathogenic variants, including gross deletions, were found in the SPG11 gene the Czech SPG11 patients, the c.3454-2A>G variant is novel