Covalent Attachment of FeFe Hydrogenases to Carbon Electrodes for Direct Electron Transfer

Direct electron transfer between enzymes and electrodes is now commonly achieved, but obtaining protein films that are very stable may be challenging. This is particularly crucial in the case of hydrogenases, the enzymes that catalyze the biological conversion between dihydrogen and protons, because the instability of the hydrogenase films may prevent the use of these enzymes as electrocatalysts of H(2) oxidation and production in biofuel cells and photoelectrochemical cells. Here we show that two different FeFe hydrogenases (from Chamydomonas reinhardtii and Clostridium acetobutylicum) can be covalently attached to functionalized pyrolytic graphite electrodes using peptidic coupling. In both cases, a surface patch of lysine residues makes it possible to favor an orientation that is efficient for fast, direct electron transfer. High hydrogen-oxidation current densities are maintained for up to one week, the only limitation being the intrinsic stability of the enzyme. We also show that covalent attachment has no effect on the catalytic properties of the enzyme, which means that this strategy can also used be for electrochemical studies of the catalytic mechanism.     

New insights into the systems for heterologous synthesis and maturation of hydrogenases,the most efficient biohydrogen producers

Biohydrogen is considered as an important key to a sustainable world power supply and is currently being seen as the versatile fuel of the future, with the potential to replace fossil fuels. The most efficient biohydrogen producers are hydrogenases. Nevertheless, due to the complex maturation processes of these enzymes, their heterologous production leaves some intriguing points not elucidated up to now. The limit of our understanding in this field makes a barrier for hydrogenases application in a variety of biotechnological processes. This review focuses on recent progresses in the development of heterologous production systems and cell-free maturation systems for the biosynthesis of active [Fe–Fe] and [Ni–Fe] hydrogenases. It also highlights some up to now un-discussed questions on the probable existence of unknown machinery able to maturate [Fe–Fe] hydrogenases or a contribution of the [Ni–Fe] hydrogenases maturases to the formation of an active H-cluster for the [Fe–Fe] hydrogenases.     

Simulation‐Experimental Approach to Investigate the Role of Interfaces in Self‐Replenishing Composite Coatings

To investigate self‐replenishing on surface‐structured composite coatings a dual simulation‐experimental approach is employed to study the decisive role of polymer‐air and polymer‐particle interfaces. Experimentally, the composite system consists of a cross‐linked polymer network with fluorinated‐dangling chains, embedding colloidal SiO₂ nanoparticles which are incorporated in the network via covalent bonding. These particles provide the desired surface structure at the air‐interface before and after damage. Any damage replicates the rough surface, while the polymer layer on top of the particles serves as source of low surface energy groups which are able to reorient towards the new air‐interfaces. Using coarse‐grained simulations details of these self‐replenishing composite systems are revealed such as the minimum thickness of the polymer layer necessary for providing optimal self‐replenishing ability and the distribution profile of the dangling chains at the various interfaces. The principles and dual approach reported here may be applied to other self‐healing composite systems with applications in self‐cleaning, anti‐fouling or low adhesion materials.     

Thin-layer high-vacuum distillation to isolate volatile flavour compounds of cocoa powder

The volatile fraction of commercial cocoa powders was isolated using thin-layer high-vacuum distillation (TLHVD) of Soxhlet extracts. Calculated and experimental recovery of the internal standard n-undecanoic acid methylester did agree, and a good reproducibility was found for the procedure. Around 70 volatile compounds were identified and semi-quantified using internal standard-based gas chromatography (GC), coupled GC–mass spectrometry (GC–MS) and GC-olfactometry (GC-O). Dehydromevalonic acid lactone, (R)-(−)-pantolactone and two diastereomer solerols were identified for the first time after purification by micropreparative GC and re-analysis using GC–MS and chiral GC. Strong sensory contributions also came from acetic acid, 2/3-methyl butanoic acid, phenylacetaldehyde, furaneol, dihydroxymaltol, vanillin and phenylacetic acid.     

Carbothermal Synthesis of α-SiC Micro-Ribbons

We report the synthesis of microscopic α-SiC ribbons (belts) on the surface of a graphite rod at 1800°–1900°C by a carbothermal process. The width of the ribbons produced ranged from 500 nm to 5 μm and the aspect ratio was up to 400. The ribbon thickness ranged from 50 to 800 nm. Their growth mechanism was explained by accelerated growth along the twin boundary. SiC whiskers grew on the rod along with the ribbons. Frequently, ribbons were growing from the tip of a whisker or whiskers were growing from the edge of a ribbon. SiC ribbons may find applications in high-temperature sensors, photo-electronic devices, or robust cantilevers in micro (or nano) electro mechanical systems. Alternatively, they can be used as reinforcements in composite materials, conferring anisotropic mechanical properties, such as unidirectional flexibility, to the composite.     

Modeling study of hydrogen production via partial oxidation of H2S–H2O blend

Kinetic analysis of the thermal partial oxidation in the H₂S–H₂O–O₂(air) mixture in a flow reactor with given length is conducted numerically on the basis of developed reaction mechanism. This mechanism incorporates the reaction paths typical both for the H₂S pyrolysis and for the H₂S oxidation and describes with reasonable accuracy a large set of experimental data. The computations have demonstrated that addition of H₂O to the fuel-rich H₂S–O₂(air) mixture allows one to increase the relative yield of H₂ in the conversion products. At identical fractions of H₂S and H₂O in the H₂S–H₂O blend the increase in the H₂ relative yield can mount to a factor of 1.5. Though the addition of H₂O to H₂S leads to the delay of the conversion of H₂S, nevertheless, at initial temperature (T₀ = 1000 K) it is possible to occur the conversion process in a shot flow reactor of 1 m length at atmospheric pressure. It has been shown that the formation of additional amount of H₂ in the conversion products upon the H₂O admixture to H₂S is caused by the increase of the role of reaction H₂O + H = OH + H₂. The growth in the initial temperature of the H₂S–H₂O–O₂(air) mixture increases the absolute concentration of H₂ in the conversion products and its relative yield.     

Facile synthesis of Ag/Zn1-xCuxO nanoparticle compound photocatalyst for high-efficiency photocatalytic degradation: Insights into the synergies and antagonisms between Cu and Ag

By carefully balancing synergies and antagonisms that arise from incorporating Cu and Ag within a single ZnO-based catalytic platform, the photocatalytic activity of Ag/ZnO based on three-dimensional modified ceramic structures can be further significantly enhanced. The performance of Ag/ZnO heterostructure (Z0) was significantly improved by only 0.2 mol% Cu incorporation (Z0.2) and the first-order degradation kinetics constants (K) of Z0.2 were 2 and 1.5 times higher than that of Z0 under simulated sunlight and UV light. The synergies between Cu dopants and metallic Ag were mainly the significantly enhanced visible light absorption capacity and the prolonged photo-excited charge lifetime. However, with the excessive introduction of Cu precursors, the surface Cu²⁺ was found to inhibit the interfacial charge transfer between Ag and ZnO NPs under UV and visible light irradiation, but the transformation from Cu²⁺ to Cu⁺ was also presumed to be a driving factor for the improvement of photocatalytic efficiency. These interactions may provide a useful pathway for enhancing photocatalytic efficiency of low-cost ZnO-based catalytic platforms.     

A Review on Ionic Liquids-Based Membranes for Middle and High Temperature Polymer Electrolyte Membrane Fuel Cells (PEM FCs)

Today, the use of polymer electrolyte membranes (PEMs) possessing ionic liquids (ILs) in middle and high temperature polymer electrolyte membrane fuel cells (MT-PEMFCs and HT-PEMFCs) have been increased. ILs are the organic salts, and they are typically liquid at the temperature lower than 100 °C with high conductivity and thermal stability. The membranes containing ILs can conduct protons through the PEMs at elevated temperatures (more than 80 °C), unlike the Nafion-based membranes. A wide range of ILs have been identified, including chiral ILs, bio-ILs, basic ILs, energetic ILs, metallic ILs, and neutral ILs, that, from among them, functionalized ionic liquids (FILs) include a lot of ion exchange groups in their structure that improve and accelerate proton conduction through the polymeric membrane. In spite of positive features of using ILs, the leaching of ILs from the membranes during the operation of fuel cell is the main downside of these organic salts, which leads to reducing the performance of the membranes; however, there are some ways to diminish leaching from the membranes. The aim of this review is to provide an overview of these issues by evaluating key studies that have been undertaken in the last years in order to present objective and comprehensive updated information that presents the progress that has been made in this field. Significant information regarding the utilization of ILs in MT-PEMFCs and HT-PEMFCs, ILs structure, properties, and synthesis is given. Moreover, leaching of ILs as a challenging demerit and the possible methods to tackle this problem are approached in this paper. The present review will be of interest to chemists, electrochemists, environmentalists, and any other researchers working on sustainable energy production field.     

Parental worry about indoor air quality and student symptom reporting in primary schools with or without indoor air quality problems

Poor indoor air quality (IAQ) in schools is related to increased symptom reporting in students. We investigated whether parental worry about school IAQ influences this association. Data came from survey collected from five Finnish primary schools with observed IAQ problems and five control schools. Parents (n = 1868) of primary school students reported worry about IAQ in schools and symptoms of their children. Associations between observed IAQ problems, worry, and five symptom scores (ie, respiratory, lower respiratory, eye, skin, and general symptoms) were analyzed using multivariate logistic regression and mediation analysis. Parents were on average more worried in schools with observed IAQ problems. Observed IAQ problems were strongly associated with increased worry and all symptoms under study (unadjusted ORs ranged between 1.48 [95% CI 1.48‐2.16] and 2.70 [95% CI 1.52‐5.17]). Parental worry was associated with all symptoms (unadjusted ORs ranged between 2.49 [95% CI 1.75‐3.60] and 4.92 [95% CI 2.77‐9.40]). Mediation analyses suggested that parental worry might partially explain the association between observed IAQ problems and symptom reporting (proportion mediated ranged between 67% and 84% for the different symptoms). However, prospective studies are needed to assess causal relationships between observed IAQ problems, worry, and symptom reporting in schools.     

20q gain associates with immortalization: 20q13.2 amplification correlates with genome instability in human papillomavirus 16 E7 transformed human uroepithelial cells

Pisatin is the major phytoalexin produced by pea upon microbial infection. The enzyme that catalyzes the terminal step in the pisatin biosynthetic pathway is (+)6a-hydroxymaackiain 3-O-methyltransferase (HMM). We report here the isolation and characterization of two HMM cDNA clones (pHMM1 and pHMM2) made from RNA obtained from Nectria haematococca-infected pea tissue. The two clones were confirmed to encode HMM activity by heterologous expression in Escherichia coli. The substrate specificity of the methyltransferases in E. coli was similar to the activity detected in CuCl2-treated pea tissue. Nucleotide sequence analysis of Hmm1 and Hmm2 revealed an open reading frame of 1080 bp and 360 amino acid residues which would encode 40.36 kda and 40.41 kDa polypeptides, respectively. The deduced amino acid sequence of HMM1 has 95.8% identity to HMM2, 40.6% identity to Zrp4, a putative O-methyltransferase (OMT) in maize root, and 39.1% to pBH72-F1, a putative OMT induced in barley by fungal pathogens or UV light. Comparison of the deduced amino acid sequences of the cDNA clones to OMTs from other higher plants identified the binding sites of S-adenosylmethionine (AdoMet). Southern blot analysis showed two closely linked genes with strong homology to Hmm in the pea genome.