Search

Reductive dissolution of barium (Ba) sulfate in wetland soils may increase Ba bioavailability in the environment, yet no information is available regarding Ba remediation using biochar. This study investigated the effectiveness of sugarcane (Saccharum officinarum) straw biochar pyrolyzed at 350 °C (BC350), 550 °C (BC550), and 750 °C (BC750) in inhibiting barite dissolution and, consequently, Ba availability in a soil artificially spiked with barite and flooded for 365 days. Increasing pyrolysis temperature alters the carbon structure, and increases dehydration and depolymerization, resulting in more stable biochar that releases less DOC (8.6-fold decrease from BC350 to BC750). Additionally, high-temperature biochar (BC750) had 1.7 times higher carbon (C) content, 2.4 times higher ash content, and a 13.1 times greater specific surface area (SSA) than low-temperature biochar (BC350). Amending soil with BC750 increased pH but did not promote reducing conditions, and thus did not promote barite dissolution. Conversely, greater DOC in low-temperature biochar, particularly BC350, favored reducing conditions and increased barite dissolution by 23%, with BC550 also showing an 18% increase. This enhancement led to a greater pool of Ba sorbed into more labile exchangeable sites. In summary, pyrolysis temperature affects biochar attributes, which in turn influences the soil geochemical environment and Ba speciation. Low-temperature biochar (BC350) shows potential as an amendment to increase the bioavailable Ba pool in assisted remediation programs, such as biochar-assisted phytoremediation. Highlights: • Biochar pyrolysis temperature affected both redox potential and barite dissolution. • BC750 mitigated barite dissolution while modifying exchangeable sorption sites. • DOC release from low temperature biochar promoted barite reductive dissolution. • BC350 may enhance biochar-mediated phytoremediation applications. [ABSTRACT FROM AUTHOR]

Imine-bridged meso-meso and β-meso unsymmetrical thien-2-yl porphyrin dyads were synthesized by condensation of meso- and β-formyl derivatives of 5,10,15,20-tetrakis(3-methylthien-2-yl)porphyrinato nickel (II), Ni3MeThP with 5-(5-Aminothien-2-yl)-10,15,20-triphenylporphyrinato nickel(II), Ni5AThPP in the presence of lanthanum(III)triflate catalyst in toluene at 120 °C for 8 h. The structural, photophysical, and redox properties were investigated by 1H NMR, UV/Vis spectral, and electrochemical analysis. The near coplanarity of the linker thien-2-yl group with the central porphyrin π-system, which can influence the electron delocalization of these molecules, is explained using electronic spectroscopy and cyclic voltammetry. The stronger electronic interaction between the two porphyrin units and the increased nonplanarity of the macrocycle brought about by the β-meso imine bridging is indicated by the larger shift of redox potentials in the dyad-2 as compared to the dyad-1 system. The results of the present investigation reveal that the two distinct porphyrin units in dyads interact via their near planar thien-2-yl linker. [ABSTRACT FROM AUTHOR]

Nitroreductases (NRs) are NAD(P)H‐dependent flavoenzymes that reduce nitro aromatic compounds to their corresponding arylamines via the nitroso and hydroxylamine intermediates. Because of their broad substrate scope and versatility, NRs have found application in multiple fields such as biocatalysis, bioremediation, cell‐imaging and prodrug activation. However, only a limited number of members of the broad NR superfamily (> 24 000 sequences) have been experimentally characterized. Within this group of enzymes, only few are capable of amine synthesis, which is a fundamental chemical transformation for the pharmaceutical, agricultural, and textile industries. Herein, we provide a comprehensive description of a recently discovered NR from Bacillus tequilensis, named BtNR. This enzyme has previously been demonstrated to have the capability to fully convert nitro aromatic and heterocyclic compounds to their respective primary amines. In this study, we determined its biochemical, kinetic and structural properties, including its apparent melting temperature (Tm) of 59 °C, broad pH activity range (from pH 3 to 10) and a notably low redox potential (−236 ± 1 mV) in comparison to other well‐known NRs. We also determined its steady‐state and pre‐steady‐state kinetic parameters, which are consistent with other NRs. Additionally, we elucidated the crystal structure of BtNR, which resembles the well‐characterized Escherichia coli oxygen‐insensitive NAD(P)H nitroreductase (NfsB), and investigated the substrate binding in its active site through docking and molecular dynamics studies with four nitro aromatic substrates. Guided by these structural analyses, we probed the functional roles of active site residues by site‐directed mutagenesis. Our findings provide valuable insights into the biochemical and structural properties of BtNR, as well as its potential applications in biotechnology. [ABSTRACT FROM AUTHOR]

The addition of biochar inevitably modifies the acidity (pH), redox potential (Eh), and dissolved organic matter (DOM) level in the soil. These alterations also have coupled effects on the cycling of iron (Fe) and the composition of bacterial communities, thereby impacting the speciation and availability of arsenic (As) in the soil. This study explored the potential mechanisms through which biochar affects As in paddy soil during flooded cultivation with different pyrolysis temperature biochars (300 °C, 400 °C, and 500 °C) added. The results revealed that the TAs concentration increased in the initial 15 days of soil cultivation with SBC300 or SBC400 addition because increasing the concentration of DOM induced the mobility of As though the formation of As-DOM complexes. Meanwhile, biochar addition elevated the pH, decreased the Eh, and promoted the transformation of specific adsorbed As (A-As) and amorphous iron oxide-bound As (Amo-Fe-As) to supernatant As through enhancing the reductive dissolution of Fe(oxy)(hydr)oxides. Moreover, the biochar altered the relative abundance of As (V)-reducing bacteria (such as Firmicutes) and As (III)-oxidizing bacteria (such as Chloroflex), thereby affecting As speciation. However, these mechanistic effects varied depending on the pyrolysis temperature of the biochar. The microbial composition of SBC300 and SBC400 were similar, with both containing larger populations of Enterobacteriaceae (AsRB) and pseudomonas (FeRB) compared to CK and SBC500. It was proposed that lower pyrolysis temperatures (300 °C and 400 °C) are more favorable for the dissolution of Fe(oxy)(hydr)oxides and the reduction of As (V). However, the biochar from the higher pyrolysis temperature (500 °C) showed environmental impacts akin to the control group (CK). This study demonstrated potential mechanisms of biochar's effect on As and the role of pyrolysis temperature. [ABSTRACT FROM AUTHOR]

AbstractEne-reductase (ER) has been widely applied for asymmetrical synthesis of chiral intermediates due to its substrate promiscuity, photoexcited reactivity, and excellent property with producing two chiral centers at a time. Natural ERs often exhibit the same stereoselectivity, and they need to be engineered for opposite configuration of chiral compounds. The hydrogenation process toward activated alkenes by ERs is composed of reductive half reaction and oxidative half reaction, which are dependent upon two cofactors NAD(P)H and flavin mononucleotide. The catalytic activity of ERs will be affected by the size of the substrate, the activating strength of the electron-withdrawing groups, redox potential of cofactors, and the loop flexibility around catalytic cavity. Currently, protein engineering to ERs has been successfully employed to enhance various catalytic properties, including photoexcited asymmetric synthesis. This review summarizes the approaches to reverse the stereoselectivity and enhance catalytic activity of ERs and new applications of the engineered ERs in photobiocatalytic asymmetric synthesis, besides the discussion with the existing molecular mechanisms of mutants regarding the improved catalytic performance. [ABSTRACT FROM AUTHOR]

Potentially harmful element (PHE) bioavailability is important to environmental contamination and must be checked under several soil conditions. This study aimed to assess Fe, Mn, and PHE uptake by rice (Oryza sativa) grown on flooded and non-flooded Fe tailings collected from the Doce River basin after its collapse in Brazil. After 65 days of sowing, shoots and roots were harvested to determine PHE concentrations. The mean concentrations of Mn in shoots and Fe in the roots of rice grown on the flooded tailings were 2140 mg kg−1 and 15,219 mg kg−1, respectively. Mn was extensively translocated from roots to shoots (translocation factor (TF) = 2). Conversely, Fe accumulated in roots (TF = 0.015) and caused morphological damage to this rice organ. The application of macro and micronutrients lessened Fe toxicity in the roots of rice cultivated on the flooded tailings. The flooding of tailings influenced more Fe accumulation than Mn accumulation by rice plants. The PHE Ag, As, Cd, Ni, Hg, Pb, and Sb exhibited low total concentrations (maximum of 9 mg kg−1 for Ni and a minimum of 0.2 mg kg−1 for Cd, Hg, and Sb), and it was not observed an increase in their availability under tailings flooding conditions. [ABSTRACT FROM AUTHOR]

Porphyrins were identified some years ago as a promising, easily accessible, and tunable class of organic photoredox catalysts, but a systematic study on the effect of the electronic nature and of the position of the substituents on both the ground-state and the excited-state redox potentials of these compounds is still lacking. We prepared a set of known functionalized porphyrin derivatives containing different substituents either in one of the meso positions or at a β-pyrrole carbon, and we determined their ground- and (singlet) excited-state redox potentials. We found that while the estimated singlet excited-state energies are essentially unaffected by the introduction of substituents, the redox potentials (both in the ground- and in the singlet excited-state) depend on the electron-withdrawing or electron-donating nature of the substituents. Thus, the presence of groups with electron-withdrawing resonance effects results in an enhancement of the reduction facility of the photocatalyst, both in the ground and in the excited state. We next prepared a second set of four previously unknown meso-substituted porphyrins, having a benzoyl group at different positions. The reduction facility of the porphyrin increases with the proximity of the substituent to the porphine core, reaching a maximum when the benzoyl substituent is introduced at a meso position. [ABSTRACT FROM AUTHOR]

Coenzyme F430 is a nickel‐containing tetrapyrrole, serving as the prosthetic group of methyl‐coenzyme M reductase in methanogenic and methanotrophic archaea. During coenzyme F430 biosynthesis, the tetrapyrrole macrocycle is reduced by the nitrogenase‐like CfbC/D system consisting of the reductase component CfbC and the catalytic component CfbD. Both components are homodimeric proteins, each carrying a [4Fe‐4S] cluster. Here, the ligands of the [4Fe‐4S] clusters of CfbC2 and CfbD2 were identified revealing an all cysteine ligation of both clusters. Moreover, the midpoint potentials of the [4Fe‐4S] clusters were determined to be −256 mV for CfbC2 and −407 mV for CfbD2. These midpoint potentials indicate that the consecutive thermodynamically unfavorable 6 individual "up‐hill" electron transfers to the organic moiety of the Ni2+‐sirohydrochlorin a,c‐diamide substrate require an intricate interplay of ATP‐binding, hydrolysis, protein complex formation and release to drive product formation, which is a common theme in nitrogenase‐like systems. [ABSTRACT FROM AUTHOR]

Redox reactions control the environmental fate of selenium, an element of concern due to its small gap between beneficial and detrimental effects on human health and due to the longevity of the radionuclide 79Se produced in nuclear reactors. Fe-bearing clay minerals are major redox-active ingredients of Earth's critical zone and constitute an important component of the barrier in (radioactive and other) waste repositories. Here we systematically investigate selenite (Se(IV)O 3 2−) sorption and reduction by Fe-bearing clay minerals of the smectite group, using batch experiments and X-ray absorption fine structure (XAFS) spectroscopy to elucidate reaction mechanisms and kinetics up to 720 or 3600 h. We found a linear relationship between structural Fe(II) content and selenite reduction rate. Selenite reduction depends also on redox potential and pH, with pH 7 showing a slower reduction rate than at pH 5. Selenite first sorbs to clay edge sites by forming an inner-sphere sorption complex, before being reduced to Se(0). The first redox product was amorphous (red) Se(0), which gradually transformed into trigonal (grey) Se(0), indicative of a kinetically hindered conversion of an amorphous (or less crystalline) solid phase into the thermodynamically stable and more crystalline form of the solid. Despite an Fe2+ aq concentration of up to 6·10−4 M in the clay suspension, and their thermodynamic prediction for the clays at lower E h , we did not observe formation of iron selenides. These insights into the selenite reduction mechanisms by Fe-bearing clays provides valuable information for the development of effective approaches for selenite immobilization. [ABSTRACT FROM AUTHOR]

High‐valent Fe(IV)=O intermediates of metalloenzymes have inspired numerous efforts to generate synthetic analogs to mimic and understand their substrate oxidation reactivities. However, high‐valent M(IV) complexes of late transition metals are rare. We have recently reported a novel Co(IV)−dinitrate complex (1‐NO3) that activates sp3 C−H bonds up to 87 kcal/mol. In this work, we have shown that the nitrate ligands in 1‐NO3 can be replaced by azide, a more basic coordinating base, resulting in the formation of a more potent Co(IV)−diazide species (1‐N3) that reacts with substrates (hydrocarbons and phenols) at faster rate constants and activates stronger C−H bonds than the parent complex 1‐NO3. We have characterized 1‐N3 employing a combination of spectroscopic and computational approaches. Our results clearly show that the coordination of azide leads to the modulation of the Co(IV) electronic structure and the Co(IV/III) redox potential. Together with the higher basicity of azide, these thermodynamic parameters contribute to the higher driving forces of 1‐N3 than 1‐NO3 for C−H bond activation. Our discoveries are thus insightful for designing more reactive bio‐inspired high‐valent late transition metal complexes for activating inert aliphatic hydrocarbons. [ABSTRACT FROM AUTHOR]

In wine technology, the on-line measurement of redox potential is a fast, accurate, and reliable measurement that provides insight into the metabolism of Saccharomyces cerevisiae, its microbial activity, and the oxidation and reduction state of wine, as well as insight into its quality and stability. The significance of the redox potential measurement and control in wine technology as well as the maintenance and regulation of fermentation redox potential using temperature and carbon dioxide fluxes are discussed. Redox potential levels from Eh 100 to 180 mV are typical for non-oxidized wine that is bottling-ready, while levels of Eh 270 to 460 mV represent oxidized wines with typical failures. The relevance of redox potential measurement during the 2-year maturation of Blau Fränkisch wine in 225 L oak barrels at six levels at a temperature 15 °C is presented. The measurement of the redox potential, expressing heterogeneity in redox layers during wine maturation in oak barrels, is represented in various oxido-reductive fermentation zones. On the contrary, the end of the maturation process is indicated by the homogeneity of redox zones, where the matured wine shows no differences in redox measurement on all levels. Using redox potential as a key scale-up criteria ensures comparable and reproducible amounts of the final product even in geometrically non-similar fermenter systems. [ABSTRACT FROM AUTHOR]

In the present study, we have investigated factors affecting the accuracy of computational chemistry calculation of redox potentials, namely the gas‐phase ionization energy (IE) and electron affinity (EA), and the continuum solvation effect. In general, double‐hybrid density functional theory methods yield IEs and EAs that are on average within ~0.1 eV of our high‐level W3X‐L benchmark, with the best performing method being DSD‐BLYP/ma‐def2‐QZVPP. For lower‐cost methods, the average errors are ~0.2–0.3 eV, with ωB97X‐3c being the most accurate (~0.15 eV). For the solvation component, essentially all methods have an average error of ~0.3 eV, which shows the limitation of the continuum solvation model. Curiously, the directly calculated redox potentials show errors of ~0.3 eV for all methods. These errors are notably smaller than what can be expected from error propagation with the two components (IE and EA, and solvation effect). Such a discrepancy can be attributed to the cancellation of errors, with the lowest‐cost GFN2‐xTB method benefiting the most, and the most accurate ωB97X‐3c method benefiting the least. For organometallic species, the redox potentials show large deviations exceeding ~0.5 eV even for DSD‐BLYP. The large errors are attributed to those for the gas‐phase IEs and EAs, which represents a major barrier to the accurate calculation of redox potentials for such systems. [ABSTRACT FROM AUTHOR]

The assessment of mineral surface hydrophobicity at the industrial scale is a challenge. In some industrial situations, such information is indirectly obtained from other proxy variables. A well-known example of this is observed in the Cu-Mo selective flotation operation, where sodium hydrosulphide is used to change the redox potential and, controlling this value, determine when Cu-sulphide floatability is inhibited. Preliminary experiments indicate that this reagent may also promote the formation of solid precipitates, reducing its impact on the redox potential. This study aims at designing a simple strategy at the laboratory scale to report and quantify NaSH losses due to parallel, irreversible, and/or fast reactions, such as precipitation. Experiments carried out using process water coming from a Cu-Mo selective flotation plant in Chile show that departing from different pH conditions and the addition of hydrosulphide ions effectively triggers the precipitation of specific metal ions, decreasing its availability to reduce the redox potential of the aqueous solution. For this specific case scenario and water quality, around 5% of the NaSH dosed precipitated. An SEM-EDX analysis of the produced solid phase shows that it is composed of mainly iron sulphide and hydroxide, along with other metal hydroxides. More importantly, it was found that dosing the reagent at the same concentration, but in the form of small increments, allows reaching the redox potential more efficiently, reducing to some extent the precipitate production and the unnecessary NaSH consumption in up to 30% of the NaSH dosed. Preliminary 1-D modelling of the process, based on mass transport coupled with reaction mechanisms, provided a first indication of the best dosing conditions for this reagent. The latter is expected to contribute to the development of better and improved reagent dosage technologies in froth flotation environments. [ABSTRACT FROM AUTHOR]

The tendency of the periplasmic redox proteins in acidophiles to have more positive redox potentials (Em) than their homologous counterparts in neutrophiles suggests an adaptation to acidic pH at protein level, since thermodynamics of electron transfer processes are also affected by acidic pH. Since this conclusion is mainly based on the electrochemical characterization of redox proteins from extreme acidophiles of the genus Acidithiobacillus, we aimed to characterize three recombinant redox proteins of the more moderate acidophile Ferrovum sp. PN-J47-F6. We applied protein film voltammetry and linear sweep voltammetry coupled to UV/Vis spectroscopy to characterize the redox behavior of HiPIP-41, CytC-18, and CytC-78, respectively. The Em-values of HiPIP-41 (571 ± 16 mV), CytC-18 (276 ± 8 mV, 416 ± 2 mV), and CytC-78 (308 ± 7 mV, 399 ± 7 mV) were indeed more positive than those of homologous redox proteins in neutrophiles. Moreover, our findings suggest that the adaptation of redox proteins with respect to their Em occurs more gradually in response to the pH, since there are also differences between moderate and more extreme acidophiles. In order to address structure function correlations in these redox proteins with respect to structural features affecting the Em, we conducted a comparative structural analysis of the Ferrovum-derived redox proteins and homologs of Acidithiobacillus spp. and neutrophilic proteobacteria. Hydrophobic contacts in the redox cofactor binding pockets resulting in a low solvent accessibility appear to be the major factor contributing to the more positive Em-values in acidophilederived redox proteins. While additional cysteines in HiPIPs of acidophiles might increase the effective shielding of the [4Fe-4S]-cofactor, the tight shielding of the heme centers in acidophile-derived cytochromes is achieved by a drastic increase in hydrophobic contacts (A.f. Cyc41), and by a larger fraction of aromatic residues in the binding pockets (CytC-18, CytC-78). [ABSTRACT FROM AUTHOR]

Carbon monoxide (CO) is a primary air pollutant and a poisonous species for human beings, animals, and some catalytic reactions. Meanwhile, CO is also a versatile feedstock in the chemical industry to produce high‐value chemicals and clean fuels, which has stimulated extensive research interests in exploiting efficient CO conversion processes. Redox potential is a key thermodynamic quantity in these processes whereas only standard reduction potentials at 25°C and 1 atm are currently available. Herein, it is the first time to report the effects of temperature (0–1000°C), pressure (1–100 atm), and adsorption on the redox potentials of 18 CO conversion reactions to form carbon dioxide, methane, straight‐chain alkanes (ethane, propane, and butane), light olefins (ethylene, propylene, and butylene), benzene, alcohols, aldehydes, acids, and dimethyl ether, based on theoretical calculations. It was noticed that gas‐phase, aqueous‐phase, and adsorption‐state redox potentials decrease with increasing temperature at an increased rate while they show different responses to pressure change. Namely, gas‐phase and most aqueous‐phase redox potentials increase with pressure at a gradually declined rate, while adsorption‐state redox potentials are not influenced by pressure. Most importantly, the significant differences up to 2.06 V under varied conditions highlight the necessity of applying operando redox potentials for CO conversion reactions. [ABSTRACT FROM AUTHOR]

Biological filtration is a complex process consisting of two consecutive stages. The nutrient transport stage, which is influenced by various fluid mechanical and surface-physical factors, represents a precondition for the biochemical process taking place within the biofilm. Biological water filtration is based on the catalyzed decomposition of contaminant molecules with the help of enzymes. This article, in addition to describing the conditions and mode of action typical within this second stage, also aims to explore the practical implications of the established results, including the controllability of biological reactors. [ABSTRACT FROM AUTHOR]

The redox potential plays a critical role in sustaining the stability of gut microbiota. This study measured the fecal redox potential in healthy and diarrheal pigs using direct and dilution methods and investigated their correlation with microbiota. The results showed that the fluctuations in the redox potential of healthy pig feces were consistent using two different methods and the two methods are equivalent based on an equivalence test. The redox potential was positively correlated with the number of fungi and negatively related to the total bacteria. The relative or absolute abundances of many bacteria at the phyla and genus levels were associated with redox potential. In diarrheal pigs, the potentiometric trends of the two methods demonstrated an opposing pattern and the correlation with total bacteria was reversed. Precipitously elevated redox potential was detected post-diarrhea using dilution methods. The absolute abundance of Escherichia-Shigella and Fuurnierella was positively correlated with redox potential, while both relative and absolute abundances of Limosilactobacillus were positively correlated. These results suggest that both methods are suitable for detecting gut redox potential in healthy pigs, while the dilution method is more suitable for diarrheal pigs. The findings on the correlation of Limosilactobacillus, Prevotella, and Escherichia-Shigella with redox potential offer novel insights for targeted modulation of intestinal health. [ABSTRACT FROM AUTHOR]

The medicinally effective plant Achillea fragrantissima exhibits a magnitude of pharmacological activities. In this study, the effects of different ZnONP concentrations on antioxidant enzymes, bioactive secondary metabolites, redox potential, and molecular changes in A. fragrantissima callus cultures were investigated. First, the concentrations of the growth regulators 2,4-D and BA were optimized using Murashige and Skoog (MS) medium. The MS medium was then administered with 2,4-D and BA at its optimal dosage (1.0 mg.L−1); afterward, different ZnONP supplements (0.0, 5.0, 10.0, 15.0, and 20.0 mg.L−1) were added. ZnONPs resulted in many physiological and molecular responses. ZnONPs significantly increased POD, APX, and SOD activities. While 10.0 mg.L−1 ZnONPs significantly increased POD and APX activities, 15.0 mg.L−1 ZnONPs significantly increased SOD. However, CAT activity gradually decreased with ZnONPs. Metabolically, ZnONPs increased phenolics, flavonoids, alkaloids, and saponin levels. Phenolic levels peaked at 20.0 mg.L−1, flavonoids at 15.0 mg.L−1, and alkaloids and saponins at 10.0 mg.L−1. Terpenoids were more prevalent at lower levels of ZnONPs. With 15.0 and 10.0 mg.L−1 giving the maximum activity, ZnONPs enhanced the DPPH activity and TAC of the callus culture extracts, respectively. RAPD and ISSR fingerprinting were applied using 12 random and ISSR primers to evaluate the genetic stability of ZnONP-induced callus cultures. Six RAPD primers showed 83% polymorphism while the seven ISSR primers achieved 30% polymorphism. Consequently, DNA mutations may have been induced by ZnONPs and caused DNA fragments to either appear or disappear in RAPD and ISSR callus profiles. The dendrogram based on RAPD and ISSR combined data showed that by increasing ZnONP concentration the genetic differentiation among callus cultures was elevated. In conclusion, higher accumulation of secondary metabolites and redox activity were increased in A. fragrantissima callus cultures using low ZnONPs (10.0 mg.L−1) concentration. [ABSTRACT FROM AUTHOR]

Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the effect of pH and the Co:Rut ratio on redox potentials and electrical conductivity of water-alcohol solutions of Co(II) complexes with rutin (Rut). It was found that the reduction potentials for the ratio Co:Rut=1:1 and 1:2 are in the range of -0.110 V to - 0.197 V relative to the Ag/AgCl reference electrode, which is significantly higher than the potentials for known flavonoids. In an alkaline medium, the absolute value of the reduction potential increases regardless of the composition of the sample. The measured range of oxidizing potentials for all compounds is in the range of +0.02 V to +0.094 V relative to Ag/AgCl reference electrode, which corresponds to the potentials of compounds with self-oxidizing activity. It is assumed that an increase in oxidative potentials up to 0.094 V can characterize the antioxidant activity, which is associated with the manifestation of the autoxidizing properties of the complex in the presence of oxygen and is due to the participation of different binding sites in chelation with the metal. Using the data of electrochemical impedance spectroscopy, the capacity of electrical double layer of a platinum electrode in water-alcohol solutions containing Co(II) complexes with rutin was calculated. An increase in capacitance values by an order of magnitude was observed at a ratio of metal:ligand=2:1 in comparison with the complexes having a ratio of 1:1. The effect of an excess of hydroxyl ions on the charge distribution at the electrode/solution interface was experimentally established, leveling the effect of the Co:Rut ratio on the electrochemical properties. [ABSTRACT FROM AUTHOR]

The results of given studies included a comparison of changes in temperature, redox potential, OH‐ions concentration and pH values in the Portland cement‐water‐additive system depending on the hydration time and features of hydration processes in the microstructure of the cement stone. The studied additives were selected taking into account the prospects for their use in the complex modifiers compositions for cement‐containing building materials. The results of electrokinetic measurements are presented and regularities and features of the influence of each studied additives on the processes of hydration structure and phase formation in Portland cement paste in the early stages of hardening are determined. The microstructure and fracture surfaces of cement stone samples formed during cement paste hardening with the optimal content of additives and features of hydration processes of cement stone were studied. The features of the mutual arrangement of individual phases in crystalline hydrate aggregates of cement stone, as well as the nature of the porosity of its microstructure, were investigated. [ABSTRACT FROM AUTHOR]

Background: The aim of this case–control study is to investigate possible associations between GSTM1 polymorphism and redox potential with sperm parameters. Methods: The study group consisted of sperm samples from 51 infertile men according to the WHO guidelines. The control group included 39 samples from men with normal seminal parameters. DNA was extracted and genotyped for the detection of the GSTM1 polymorphism. An evaluation of the static redox potential (sORP) using the MiOXSYSTM system was conducted. Results: The frequency of the GSTM1-null genotype was higher in infertile male individuals (60.78%) than in the controls (41.03%) and was associated with a 2.228-fold increased risk for male infertility. Fertile controls carrying the GSTM1-null genotype presented a lower percentage of typical sperm morphology and lower slow progressive motility. An excess of redox potential was observed in infertile males compared to fertile ones. In the control group higher sORP values had a positive correlation with immotility percentage and a negative correlation regarding total motility. In the study group sORP values had a negative correlation with total count, concentration, and slow progressive motility. Conclusions: The present study highlights that GSTM1 polymorphism and redox potential affect both fertile and in fertile males. Moreover, redox potential levels could be used as an additional indicator along with the routine semen analysis for a comprehensive screening between infertile and fertile men. [ABSTRACT FROM AUTHOR]

The gene for a previously unexplored two-domain laccase was identified in the genome of actinobacterium Streptomyces carpinensis VKM Ac-1300. The two-domain laccase, named ScaSL, was produced in a heterologous expression system (Escherichia coli strain M15 [pREP4]). The enzyme was purified to homogeneity using affinity chromatography. ScaSL laccase, like most two-domain laccases, exhibited activity in the homotrimer form. However, unlike the most two-domain laccases, it was also active in multimeric forms. The enzyme exhibited maximum activity at 80°C and was thermally stable. Half-inactivation time of ScaSL at 80°C was 40 min. The laccase was able to oxidize a non-phenolic organic compound ABTS at a maximum rate at pH 4.7, and to oxidized a phenolic compound 2,6-dimethoxyphenol at a maximum rate at pH 7.5. The laccase stability was observed in the pH range 9-11. At pH 7.5, laccase was slightly inhibited by sodium azide, sodium fluoride, and sodium chloride; at pH 4.5, the laccase was completely inhibited by 100 mM sodium azide. The determined Km and kcat of the enzyme for ABTS were 0.1 mM and 20 s–1, respectively. The Km and kcat for 2,6-dimethoxyphenol were 0.84 mM and 0.36 s–1, respectively. ScaSL catalyzed polymerization of humic acids and lignin. Redox potential of the laccase was 0.472 ± 0.007 V. Thus, the ScaSL laccase is the first characterized two-domain laccase with a middle redox potential. Crystal structure of ScaSL was determined with 2.35 Å resolution. Comparative analysis of the structures of ScaSL and other two-domain laccases suggested that the middle potential of ScaSL may be associated with conformational differences in the position of the side groups of amino acids at position 230 (in ScaSL numbering), which belong to the second coordination sphere of the copper atom of the T1 center. [ABSTRACT FROM AUTHOR]

Transition metal complexes are a promising class of redox mediators for targeting redox flow batteries due to the tunability of their electrochemical potentials. However, reliable time‐efficient tools for the prediction of their reduction potentials are needed. In this work, we establish a suitable density functional theory protocol for their prediction using an initial experimental data set of aqueous iron complexes with bidentate ligands. The approach is then cross‐validated using different complexes found in the redox‐flow literature. We find that the solvation model affects the prediction accuracy more than the functional or basis set. The smallest errors are obtained using the COSMO‐RS solvation model (mean average error (MAE)=0.24 V). With implicit solvation models, a general deviation from experimental results is observed. For a set of similar ligands, they can be corrected using simple linear regression (MAE=0.051 V for the initial set of iron complexes). [ABSTRACT FROM AUTHOR]

[Objectives] The paper aimed to study the effects of new herbicidal compounds derived from TSC-3, Taiwanin Hand Taiwanin E on the redox potential of Arabidopsis root tip cells. [Methods] The effects of different concentrations of new herbicides on the redox potential of root cap, meristematic zone, transition zone and elongation zone of Arabidopsis thaliana were determined by using mt-roGFPI A. transgenic. [Results] Different concentrations of TSC-3, Taiwanin H and Taiwanin E could reduce the redox potential of root tip cells of the mt-roGFP1 labeled transgenic Arabidopsis thaliana plants, with the increase of the concentration of the compound, the greater the effect on the redox potential of the meristem zone of mt-roGFPI labeled transgenic A. thaliana plants. After being treated with TSC-3 at 0.1,1,5 and 10 µg mL-1 the mean values of the maximum variation in redox potential changes in root cells of the meristem zone were 13.06, 18.59, 27.74 and 29.92 mV, respectively. When treated with Taiwanin H and Taiwanin E at 1, -1 5 and 10 µg mL-1, the mean values of the maximum variation of redox potential in root cells of the meristem zone were 12.21, 15.72, 22.67 mV and 14.71, 24.03, 28.69 mV, respectively. [Conclusions] In a certain range, the greater the concentration of TSC-3, Taiwanin H and Taiwanin E, the greater of the redox potential changes in root cells of the meristem zone. It indicated that the redox potential response of A. thaliana root tip cells to these herbicidal compounds was dose-response related. Our results provide a basis for the study of the mechanism of novel plant-derived herbicides on root cell mitochondria by roGFPI fluorescence probe technology, and they also provide theoretical basis for the establishment of a rapid screening platform for herbicidal compounds. [ABSTRACT FROM AUTHOR]

In recent years, there has been considerable interest in the potential of quinones as a promising category of electroactive species for use in aqueous organic redox flow batteries. These materials offer tunable properties and the ability to function as both positive and negative electrolytes, making them highly versatile and suitable for a range of applications. Ongoing research has focused on improving the stability, solubility, and performance of quinones, with a particular emphasis on the creation of stable negolytes. The pairing of these advancements with alternate chemistries has created new prospects for commercial applications. However, challenges persist regarding the stability of quinones in high‐potential electrolytes and the limited number of viable quinones available. Despite these obstacles, significant strides have been made, and the potential for quinones to revolutionize energy storage technology is vast. This review article provides a comprehensive overview of recent progress in this area, with a specific focus on redox potential, solubility, and stability, and offers valuable insights into the future of quinone‐based aqueous organic redox flow batteries. [ABSTRACT FROM AUTHOR]

Flavodoxins are enzymes that contain the redox-active flavin mononucleotide (FMN) cofactor and play a crucial role in numerous biological processes, including energy conversion and electron transfer. Since the redox characteristics of flavodoxins are significantly impacted by the molecular environment of the FMN cofactor, the evaluation of the interplay between the redox properties of the flavin cofactor and its molecular surroundings in flavoproteins is a critical area of investigation for both fundamental research and technological advancements, as the electrochemical tuning of flavoproteins is necessary for optimal interaction with redox acceptor or donor molecules. In order to facilitate the rational design of biomolecular devices, it is imperative to have access to computational tools that can accurately predict the redox potential of both natural and artificial flavoproteins. In this study, we have investigated the feasibility of using non-equilibrium thermodynamic integration protocols to reliably predict the redox potential of flavodoxins. Using as a test set the wild-type flavodoxin from Clostridium Beijerinckii and eight experimentally characterized single-point mutants, we have computed their redox potential. Our results show that 75% (6 out of 8) of the calculated reaction free energies are within 1 kcal/mol of the experimental values, and none exceed an error of 2 kcal/mol, confirming that non-equilibrium thermodynamic integration is a trustworthy tool for the quantitative estimation of the redox potential of this biologically and technologically significant class of enzymes. [ABSTRACT FROM AUTHOR]

N‐functionalized pyridinium frameworks derived from the three major vitamers of vitamin B6, pyridoxal, pyridoxamine and pyridoxine, have been screened computationally for consideration as negative electrode materials in aqueous organic flow batteries. A molecular database including the structure and the one‐electron standard reduction potential of related pyridinium derivatives has been generated using a computational protocol that combines semiempirical and DFT quantum chemical methods. The predicted reduction potentials span a broad range for the investigated pyridinium frameworks, but pyridoxal derivatives, particularly those involving electron withdrawing substituents, have potentials compatible with the electrochemical stability window of aqueous electrolytes. The stability of radicals formed upon one‐electron reduction has been analyzed by a new computational tool proposed recently for large‐scale computational screening. [ABSTRACT FROM AUTHOR]

Density functional theory is applied to account the ligand effect on modification in the redox potential of coordination of three NN bidentate ligands (bpy/phen) to the metal ion (Fe2+/3+/Co2+/3+). Also, the role of the ligand framework for the stabilization of [M(bpy/phen)3]2+/3+ species is discussed in detail. In this work, we have found that the M2+ ions are more stabilized with the bpy ligands while the M3+ ions are more stable with the phen ligands. The electronic structure and geometrical study disclosed the electronic configurations of the metal ions in both the possible spin states of a species. Furthermore, the HOMO–LUMO analysis demonstrates that the M3+ ion coordinated species have more energy gap as compared to the M2+ ion coordinated species. Among all the species, HOMO–LUMO energy gap has been found highest (4.62 eV) in the [Fe(bpy)3]3+ whereas lowest (3.28 eV) in the [Co(phen)3]2+ species. Additionally, we have also found that the bpy coordinated species have relatively higher redox potential value as compared to phen ligated species. Here we have noticed a close relationship between the redox potential and the optimized structural parameters of the studied species. Also, all the computed structural parameters of the studied species are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

This review summarises literature data on redox potential (Eh) as an essential characteristic of surface waters affecting their ecological and chemical state. We consider the influence of Eh on the migration of nutrients, metals, and metalloids in the 'bottom sediments – water' system and its role in the secondary pollution of water bodies. Hypoxia, anaerobic conditions, and reduced Eh leads to an increase in the concentration of nutrients, reduced forms of manganese and iron, due to their migration from bottom sediments to the aquatic environment. This, in turn, contributes to enhanced eutrophication of water bodies. We reviewed the data on the transformation of metal and metalloid compounds depends on the intensity of redox processes resulting their bioavailability, and toxicity to aquatic organisms. Humic substances, as the most common group of dissolved surface water organic substances, exhibit reducing properties and affect the coexisting metals and metalloid species. The intensity of redox processes in surface water will increase under climate change. The issue of redox transformation of elements will need to be considered in the context of developing measures to reduce surface water loading with primarily nutrients and metals, taking into account the possibility of internal pollution of water bodies. [ABSTRACT FROM AUTHOR]

Cu2+/1+ complexes facilitate the reduction of CO2 to valuable chemicals. The catalytic conversion likely involves the binding of CO2 and/or reduction intermediates to Cu2+/1+, which in turn could be influenced by the electron density on the Cu2+/1+ ion. Herein we investigated whether modulating the redox potential of Cu2+/1+ complexes by changing their ligand structures influenced their CO2 reduction performance significantly. We synthesised new heteroleptic Cu2/1+ complexes, and for the first time, studied a (Cu-bis(8-quinolinolato) complex, covering a Cu2+/1+ redox potential range of 1.3 V. We have found that the redox potential influenced the Faradaic efficiency of CO2 reduction to CO. However, no correlation between the redox potential and the Faradaic efficiency for methane was found. The lack of correlation could be attributed to the presence of a Cu-complex-derived catalyst deposited on the electrodes leading to a heterogeneous catalytic mechanism, which is controlled by the structure of the in situ deposited catalyst and not the redox potential of the pre-cursor Cu2+/1+ complexes. [ABSTRACT FROM AUTHOR]

Oxidation–reduction (redox) ladders are a fundamental biogeochemical concept that explain basic and applied phenomena including microbial metabolic evolution and chemical pollution remediation. However, it is difficult to measure and predict which redox couples dominate an environment. This discrepancy manifests a redox paradox: while redox ladders are a fundamental biogeochemical concept, it is difficult to use existing measurements to predict which redox couples dominate in an environment or use redox to predict biogeochemical state changes. Additionally, there is often confusion around the concept due to the differential emphasis in biological vs. geochemical sub-disciplines in explanations of the: (1) roles of actual vs. standard free energy calculations, (2) thermodynamics vs. enzymatic kinetics in reactions, (3) ubiquity of alternative electron donors as opposed to assuming processes are solely driven by organic carbon, and (4) difference between redox intensity and redox buffering capacity. Redox buffering capacity is a particularly underdeveloped concept within biogeochemical studies, which have largely used redox potential, a measurement with myriad analytical concerns. We review the small number of studies that have quantified redox buffering capacity. We highlight four challenges to overcome before redox buffering capacity can be a useful concept. Measuring redox buffering capacity may be key to understanding the ability of the ecosystems to resist change in redox conditions. Biogeochemists are often most interested in predicting these state changes to understand hot spot/hot moment phenomena such as greenhouse gas fluxes; thus, incorporating redox buffering capacity into our predictive frameworks and methodological toolbox may be key to unlocking the redox paradox. We postulate that the well-known ecological resilience and resistance framework constitutes the needed theoretical foundation on which measurements of redox buffering capacity can be incorporated. [ABSTRACT FROM AUTHOR]

Based on the unique ubiquity of similar solvate structures found in solvate crystals and superconcentrated electrolytes, we performed a systematic study of four reported solvate crystals which consist of different lithium salts (i.e., LiMPSA, LiTFSI, LiDFOB, and LiBOB) solvated by acetonitrile (MeCN) based on first principles calculations. Based on the calculations, these solvate crystals are predicted to be electronic insulators and are expected to be similar to their insulating liquid counterpart (e.g., 4 M superconcentrated LiTFSI-MeCN electrolyte), which has been confirmed to be a promising electrolyte in lithium batteries. Although the MeCN molecule is highly unstable during the reduction process, it is found that the salt-MeCN solvate molecules (e.g., LiTFSI-(MeCN)2, LiDFOB-(MeCN)2) and their charged counterparts (anions and cations) are both thermodynamically and electrochemically stable, which can be confirmed by Raman vibrational modes through the unique characteristic variation in C≡N bond stretching of MeCN molecules. Therefore, in addition to the development of new solvents or lithium salts, we suggest it is possible to utilize the formation of superconcentrated electrolytes with improved electrochemical stability based on existing known compounds to facilitate the development of novel electrolyte design in advanced lithium batteries. [ABSTRACT FROM AUTHOR]

Copyright of Journal of the American Institute for Conservation is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The midpoint single-electron reduction potential of nitroaromatic compounds in aqueous medium at pH 7.0 (potential of ArNO2/ArNO2·– couple, Em7) frequently determines their therapeutic and/or toxic properties. However, its estimation remains a complex problem. We propose a modified method of Em7 estimation by quantum mechanical calculations, based on the use of the dielectric continuum model together with a certain number of H2O molecules at the vicinity of nitro group. The optimal number of H2O molecules corresponds to a minimal difference between the experimentally determined and calculated values of Em7, and/or the most negative value of calculated Em7. This enabled us to calculate the Em7 values for a number of ArNO2 (n = 19) with the average deviation of 0.027 V from the experimentally determined ones. Apart from nitrobenzene derivatives, the application of this approach for the representatives of nitropyridines, nitrofurans, nitrothiophenes, and nitrothiazoles was demonstrated. In this case, nitroimidazole derivatives are an exception, evidently due to a strong proton accepting properties of N3 atom of their free radicals. [ABSTRACT FROM AUTHOR]

Methane (CH4) is the primary component of natural gas and a powerful greenhouse gas. CH4 can be utilized as an important raw material to produce value‐added chemicals via catalytic partial oxidation, oxidative/non‐oxidative coupling, steam reforming, dry reforming, etc. Redox potential is a key thermodynamic quantity in these processes while currently, only standard reduction potentials at 25°C and 1 atm are available. Herein, this is the first time to report the temperature (0–1000°C), pressure (1–100 atm), and adsorption‐dependent redox potentials of 13 CH4 oxidation reactions to generate methyl radical, methanol, methyl hydroperoxide, formaldehyde, formic acid, carbon monoxide, carbon dioxide, ethane, ethylene, ethanol, acetaldehyde, acetic acid, and benzene. It was found that redox potentials of all states (gaseous, aqueous, and adsorption states) decrease with temperature at an accelerated rate but show different responses to pressure change. Namely, while gas‐phase and aqueous‐phase redox potentials increase and decrease with pressure at a gradually declined rate, respectively, adsorption‐state redox potentials are insensitive to pressure. Most importantly, the significant differences up to 1.92 V under varied conditions reveal the necessity of applying operando redox potentials for CH4 oxidation reactions that are enabled by this report as an enriched database for broad applications. [ABSTRACT FROM AUTHOR]

Visible light photocatalysis has established itself as a promising sustainable and powerful strategy to access reactive intermediates, i.e. radicals and radical ions, under mild reaction conditions using visible light irradiation. This field enables the development of formerly challenging or even previously inaccessible organic transformations. In this tutorial review, an overview of the essential concepts and techniques of visible-light-mediated chemical processes and the most common types of photochemical activation of organic molecules, i.e. photoredox catalysis and photosensitization, are discussed. Selected photocatalytic alkene functionalization reactions are included as examples to illustrate the basic concepts and techniques with particular attention given to the understanding of their reaction mechanisms. 1 Introduction 2 Photocatalysts 3 Photophysical and Electrochemical Properties 3.1 Excited-State Energy 3.2 Ground-State Redox Potentials 3.3 Excited-State Redox Potentials 3.4 Local Absorbance Maximum for Lowest Energy Absorption 3.5 Excited-State Lifetime 3.6 [Ru(bpy)3 ]2+ as a Case Study 3.7 Basic Laws and Equations of Photochemistry and Photocatalysis 3.8 Common Terminology in Photochemistry and Photocatalysis 4 Activation Modes in Photocatalysis 4.1 Photoinduced Electron Transfer 4.2 Photoinduced Energy Transfer 5 Conclusions and Outlook [ABSTRACT FROM AUTHOR]

L-ascorbic acid is a molecule used in the hydroxylation of various biochemical reactions in cells. Its main function is the hydroxylation of collagen, the fibrillar protein that gives resistance to bones, teeth, tendons and walls of blood vessels. Furthermore, it is a powerful antioxidant, being used to transform reactive oxygen species into inert forms. It is also used in the synthesis of some molecules that serve as hormones or neurotransmitters. In this review, a series of reactions are presented and discussed with the aim to discuss as some chemical parameters such as pH, redox potential, presence of different metal ions and ascorbic acid works effectively as a ligand. Several mechanisms are revisited and aspects as the effect of transition metals over the redox chemistry of acid is presented. [ABSTRACT FROM AUTHOR]

Electroactivation is an emerging method of non-residual processing of secondary dairy products, namely, whey with high protein content, which presents one of the directions that describe the treatment of whey with different initial protein content and the extraction of serum proteins into protein mineral concentrates. The treatment of whey with high protein content was carried out in different electrolyzers with different ratios of the processed whey volume to the electrode/cathode surface and different geometric shapes, different distances between the electrodes and the membrane, which influences the specific energy consumption per unit volume. The main objective of the work was the maximum extraction of whey proteins in protein mineral concentrates and the simultaneous isomerization of lactose into lactulose at low energy consumption and the exclusion of "dead"/inefficient areas for the electroactivation of whey in different diaphragm electrolyzers. The mechanisms of whey protein extraction depending on pH and redox potential values upon electrochemical activation of whey with high protein content are presented. [ABSTRACT FROM AUTHOR]

Alluvial soils are a special product of pedolithogenesis, which takes place in floodplain conditions. Their formation is associated with the passage of floodplain and flood processes. This leads to the formation of soils that have maximum biogenicity and fertility levels. Changes in the conditions of soil formation during the year (changes in the level and composition of groundwater, the presence or absence of floods, features of the activity of the biological factor) cause changes in the physical and chemical parameters of soils, the intensity of the passage of biochemical processes, which is necessarily reflected in redox processes. This relationship is not only direct, but also reverse. The indicators of the redox potential of alluvial soils of the floodplains of the rivers of the Siversky Donets basin are given in the article. They were determined by the seasons of the year in layers at depths from 0 to 40 cm. The ORP level was determined in the field using the potentiometric method. Both for soil layers and for the seasons of the year, the indicators of the redox potential indicate the passage of reduction processes, and only in summer these processes can have the character of low-intensity oxidation. The restoration processes in the soil are most intense in spring. The bog alluvial soils of the near-Teras depression are characterized by more pronounced processes of reduction, as evidenced by the minimum values of the redox potential. [ABSTRACT FROM AUTHOR]

Molten NaCl–CaCl2–UCl3 was dosed with small amounts of NiCl2 at 600 °C to cause the redox potential to spike upwards. A metallic zirconium rod was used as the working electrode (WE) and was shorted to a stainless steel beaker [counter electrode (CE)] used to contain the salt through a potentiostat operating in zero resistance ammeter mode. The potentiostat simultaneously measured electric current between the WE and CE and the potential of the WE versus a Ag/AgCl reference electrode. With each dosing of NiCl2, the current spiked indicating oxidation of the Zr metal rod, and its open circuit potential spiked and then returned to its initial value or lower. Based on these results, in a molten salt system such as an electrorefiner or molten salt reactor where Zr metal can be an effective redox buffer, this device can be used to continuously monitor the rate at which redox buffering is occurring. [ABSTRACT FROM AUTHOR]

Catalytic conversion of carbon dioxide (CO2) into value‐added chemicals and fuels can not only mitigate global warming but also alleviate the energy crisis caused by fossil fuel depletion. Redox potential is a key thermodynamic quantity of CO2 reduction reactions, while currently, only standard reduction potential (25°C, 1 atm, 1 M) is available for application. Herein, it is the first time to report the influence of temperature (0–1000°C), pressure (1–100 atm), and molecular adsorption on the redox potentials of a series of CO2 reduction reactions to form carbon monoxide, formic acid, formaldehyde, methanol, methane, oxalic acid, acetic acid, acetaldehyde, ethanol, ethylene, and ethane. Although almost all gas‐phase and aqueous‐phase redox potentials decrease with the temperature at an increased rate and increase with pressure at a decreased rate, adsorption‐state redox potentials are only sensitive to temperature and no smaller than gas‐phase redox potentials. Significant differences of up to 2.35 V with regard to the standard reduction potential would directly affect the thermodynamics and kinetics of reactions. This report will serve as an enriched database of redox potentials for CO2 reduction reactions that allows the use under actual experimental conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel workflow is proposed to calculated ionic redox potential. • Machine learning (ML) molecular dynamics method is conducted in the workflow. • Free energy perturbation theory (FEP) calculates free energy differences. • The workflow enables larger-scale MD simulation to calculate redox potential. • Using industrial magnesium electrolysis to verify the workflow reliability. The simulation of redox potentials in molten salts faces challenges in achieving large-scale automation, limiting the accuracy and flexibility of molecular dynamics predictions. This paper proposes a novel and accurate workflow for predicting redox potentials using deep neural networks, free energy perturbation theory, and large-scale machine learning molecular dynamics. Feasibility and accuracy of the workflow are validated by using industrial magnesium electrolysis, comparing results with cyclic voltammetry curves. Maximum simulated error is just 0.3 V. Training the potential energy surface models and exploring solvation structure and energy distribution are integral to our research process. Our trained models exhibit DFT-level accuracy, with energy and force errors of 10-4 and 10-2 orders of magnitude, respectively. Solvation structure investigation reveals that introducing La3+ can release Mg2+ from MgO. A linear correlation between the free energy difference and temperature is observed. This workflow addresses the mismatch between scale and accuracy in predicting redox potentials. [ABSTRACT FROM AUTHOR]

Storing hydrogen underground for cyclic injection/retrieval may help move the world towards a decarbonised economy. In search of suitable long-term reservoirs, the potential reactivity of the matrix with hydrogen plays a major role. This is especially poignant for carbonate minerals, due to their abundance, ubiquity, and much faster dissolution kinetics compared to silicates. Geochemical modelling studies invariably find hydrogen-induced reductive carbonate dissolution and methane production (HIRCDAMP) whereas experimental studies, for the most part, do not support this view. To answer the question of how far injected hydrogen may oxidise, protonate and cause reductive dissolution of carbonates, a thermodynamic approach based on standard redox and overall cell potentials, as well as Gibbs free energies, was chosen. Together with observations on kinetic constraints, a consistent picture emerges in which purely inorganically driven reduction of (bi)carbonate to methane by hydrogen oxidation is not likely to occur. Rather, the formation of intermediate carbon species (e.g., formate) could be a kinetically and thermodynamically more favourable pathway than that to methane. It follows that geochemical models that question the long-term viability of hydrogen injection into carbonate-bearing reservoirs need to be revised, toning down any alleged, yet by experimental studies not substantiated, hydrogen reactivity in the absence of any catalyst and/or microbial activity. [Display omitted] [ABSTRACT FROM AUTHOR]

• A series of 16 compounds were synthesised and characterised, including X-ray analysis. • The redox potentials of the ferrocene amides were determined by cyclic voltammetry. • The 6-31G* and 6-311+G* base sets were employed to calculate the redox potentials. • The DFT calculation data showed a good correlation with the experimental results. Herein we report on the synthesis and characterization of a number of the simplest ferrocenes, namely Fc-amides (4a-i), Fc-amines (5a-i) and Fc-alcohol (1), as starting materials for the synthesis of redox-active ferrocene-modified compounds. Suitable conditions allowed preparing a seria of various ferrocenes with aliphatic and aromatic substituents in good to high yields. The title products were characterized by 1H, 13C NMR, IR, ESI-MS analytical methods. The structure of ferrocenyl(ortho -chlorophenyl) methanol (1) was determined by single-crystal X-ray diffraction. Geometrical parameters in compound 1 were calculated using the ab initio MP2/6-31G* method and based on the advanced DFT calculations, DFT wb97xd/6-31G* and DFT wb97xd/6-311+G*. Electrochemical investigations by cyclic voltammetry revealed reversible redox processes for the ferrocenyl amides. Potentials were also calculated using two basis sets, 6-31G* and 6-311+G*, and demonstrated a high degree of correlation with experimental results. [Display omitted] [ABSTRACT FROM AUTHOR]

The activity of lithium ions in electrolytes depends on their solvation structures. However, the understanding of changes in Li+ activity is still elusive in terms of interactions between lithium ions and solvent molecules. Herein, the chelating effect of lithium ion by forming [Li(15C5)]+ gives rise to a decrease in Li+ activity, leading to the negative potential shift of Li metal anode. Moreover, weakly solvating lithium ions in ionic liquids, such as [Li(TFSI)2]− (TFSI = bis(trifluoromethanesulfonyl)imide), increase in Li+ activity, resulting in the positive potential shift of LiFePO4 cathode. This allows the development of innovative high energy density Li metal batteries, such as 3.8 V class Li | LiFePO4 cells, along with introducing stable biphasic electrolytes. In addition, correlation between Li+ activity, cell potential shift, and Li+ solvation structure is investigated by comparing solvated Li+ ions with carbonate solvents, chelated Li+ ions with cyclic and linear ethers, and weakly solvating Li+ ions in ionic liquids. These findings elucidate a broader understanding of the complex origin of Li+ activity and provide an opportunity to achieve high energy density lithium metal batteries. [ABSTRACT FROM AUTHOR]

Aquatic environmental microbial biofilms grow in a broad range of redox environments from oxic to methanogenic, and they often also establish internal redox gradients. In technical applications, biofilms are also subjected to controlled redox conditions. Studies on biofilms often make use of fluorescence microscopic imaging techniques together with lectin binding analysis to gain insights into structure, composition, and functions of the biofilms. Here we studied the direct influence of redox potentials on fluorescence lectin binding analyses (FLBA) for two commonly used lectin-fluorophore conjugates. An effect of the electrical potential on signal intensity was observed and found to be statistically significant. The signal intensity changes however, remained within the range of a few percent total. A significant drop in intensity was only observed for extremely oxidizing potentials, typically not found under environmental conditions. Our results showed that the fluorophore itself and not the lectin binding to the respective glycoconjugate causes fluorescence changes. The two tested lectin-fluorophores are shown to be suitable for studying the distribution and composition of EPS in environmental biofilms or technical applications and under varying redox conditions. [ABSTRACT FROM AUTHOR]

This study evaluates the effect of using frozen curd on the chemical characteristics and oxidative modifications of Mozzarella cheese. Samples of Buffalo Mozzarella cheese with different frozen curd contents (0%, 5%, 20% and 50% w/w) were produced in three dairies and analysed after 1 and 9 days. Spectra of Mozzarella samples also were acquired by near‐infrared spectyoscopy. By increasing the frozen curd content, the fat content and antioxidant activity of the Mozzarella cheese were reduced. During storage, the increase in moisture content and the reduction in fat and protein content occurred. The redox potential of Mozzarella was positive and increased over time. [ABSTRACT FROM AUTHOR]

Petrochemical plants constitute the main sources of rare earth elements (REEs) in the Musa estuary. Under different redox conditions, the accumulated REEs in sedimentary beds might be released into the water column. An automated biogeochemical microcosm system was utilized to simulate reducing conditions. The effect of redox potential (Eh) on the release of REEs in an estuarine sediment sample was investigated. REEs were released from sediments by reducing Eh, and the average amount of REEs mobilization was 31.03%. When Eh was decreased from 120 to −150 mV, a decrease in pH (from 8.08 to 6.66), an increase in dissolved organic carbon (DOC) (from 18.93 to 704.84 mg/L), and an increase in the dissolution of Fe–Mn oxy-hydroxides occurred. Lu, Sm, and Pr were the most mobile elements with over 40% release rate, while Ce showed the lowest amount of release. The cluster analysis and principal component analysis exhibited that the indirect effect of Eh via the linked changes of DOC and chemistry of Fe–Mn influenced the solubility and release of REEs. Enrichment factors (EFs) revealed that the Musa estuary is threatened by Ce, Dy, La, Nd, Pr, and Sm. Since the ecotoxicological effects of dissolved REEs cause environmental risk and health issues, serious consideration needs to be given to the high potential mobility of REEs. [ABSTRACT FROM AUTHOR]

All-organic Li-ion batteries appear to be a sustainable and safer alternative to the currently-used Li-ion batteries but their application is still limited due to the lack of organic compounds with high redox potentials toward Li+/Li0. Herein, we report a computational design of nickel complexes and coordination polymers that have redox potentials spanning the full voltage range: from the highest, 4.7 V, to the lowest, 0.4 V. The complexes and polymers are modeled by binding low- and high-oxidized Ni ions (i.e., Ni(II) and Ni(IV)) to redox-active para-benzoquinone molecules substituted with carboxyl- and cyano-groups. It is found that both the nickel ions and the quinone-derived ligands are redox-active upon lithiation. The type of Ni coordination also has a bearing on the redox potentials. By combining the complex of Ni(IV) with 2-carboxylato-5-cyano-1,4-benzoquinones as a cathode and Ni(II)-2,5-dicarboxylato-3,6-dicyano-1,4-benzoquinone coordination polymer as an anode, all-organic Li-ion batteries could be assembled, operating at an average voltage exceeding 3.0 V and delivering a capacity of more than 300 mAh/g. [ABSTRACT FROM AUTHOR]

In the structure of photosynthetic reaction center (RC) of the purple bacterium Cereibacter sphaeroides the highly conserved amino acid residue Ile-M206 is located near the bacteriochlorophyll dimer P, which is the primary electron donor, and the monomeric bacteriochlorophyll BA, which is the nearest electron acceptor. Since Ile-M206 is close to the C2-acetyl group of bacteriochlorophyll PB, the hydroxyl group of Tyr-M210, and to the C9-keto group of bacteriochlorophyll BA, as well as to the water molecule near the latter group, this site can be used for introducing mutations in order to study mechanisms of primary photochemical processes in the RC. Previously it was shown that the Ile→Glu substitution at the M204 position (analog of M206 in the RC of C. sphaeroides) in the RC of the closely related purple non-sulfur bacterium Rhodobacter capsulatus significantly affected kinetics of the P+HA– state formation, whereas the M204 Ile→Gln substitution led to the loss of BChl BA molecule from the complex structure. In the present work, it is shown that the single I(M206)Q or double I(M206)Q + F(M208)A amino acid substitutions in the RC of C. sphaeroides do not change the pigment composition and do not markedly influence redox potential of the primary electron donor. However, substitution of Ile M206 by Gln affected positions and amplitudes of the absorption bands of bacteriochlorophylls, increased lifetime of the primary electron donor P* excited state from 3.1 ps to 22 ps, and decreased quantum yield of the P+QA– state formation to 60%. These data suggest significant changes in the pigment–protein interactions in the vicinity of the primary electron donor P and the nearest electron acceptor BA. A considerable decrease was also noticed in the resistance of the mutant RC to thermal denaturation, which was more pronounced in the RC with the double substitution I(M206)Q + F(M208)A. This was likely associated with the disruption of the dense packing of the protein near bacteriochlorophylls PB and BA. Possible reasons for different effects of identical mutations on the properties of two highly homologous RCs from closely related purple non-sulfur bacteria are discussed. [ABSTRACT FROM AUTHOR]