Oxygen Acceptor Research Articles

Quasi-Hydrogen Bond and Charge-Trapping Effect Originating from Polar Side Group Lead to Significantly Suppressed Charge Transport in Polypropylene.

How to fundamentally suppress charge transport is one of the essential issues in polymer dielectrics. This work reports significant charge transport suppression by glycidyl methacrylate (GMA) side group modification on polypropylene (PP). Experimental and computational investigations discover for the first time a quasi-hydrogen bond effect generated by carbonyl and epoxide of GMA in PP inter/intramolecular structure, while introducing trap energy levels within the HOMO-LUMO gap. These energy levels suppress the leakage current of GMA-modified PP thanks to the charge-trapping effect. The quasi-hydrogen bond originating from the interaction between the high-polar GMA group and flexible PP chain raises the thermostability while averaging the electron distribution between hydrogen and acceptor oxygen, which is conducive to lessening electric weak points, suppressing charge transport, and finally enhancing the electrical breakdown strength. This work provides new thinking on polymer dielectric design and charge transport regulation utilizing electron structure and weak interaction at the molecular scale.

Sputter-Deposited copper iodide thin film transistors with low Operating voltage

This paper reports on a back-gated p-type thin film transistor (TFT) with copper iodide (CuI) as the channel material, a HfO2 gate dielectric layer, and Al2O3 passivation. The γ-CuI channel was deposited from a CuI target using DC magnetron sputtering at room temperature. Our TFT can be fully shut off by VG = 4 V, with a field-effect channel hole mobility μh ∼ 1.5–2 cm2 V−1 s−1. An anneal in forming gas was performed twice, once at 200 °C, then at 250 °C to improve gate control, yielding a final Ion/Ioff current ratio of ∼ 250. The anneal served two purposes: to reduce the oxygen acceptor density in the CuI channel and reduce the concentration of interface states between the CuI, Al2O3 passivation, and HfO2. A model of the device was built in an industrial TCAD simulator, which reproduces the measured characteristics and allows an estimation of interface state densities and channel doping.

Long-distance electron transport in multicellular freshwater cable bacteria.

Filamentous multicellular cable bacteria perform centimeter-scale electron transport in a process that couples oxidation of an electron donor (sulfide) in deeper sediment to the reduction of an electron acceptor (oxygen or nitrate) near the surface. While this electric metabolism is prevalent in both marine and freshwater sediments, detailed electronic measurements of the conductivity previously focused on the marine cable bacteria (Candidatus Electrothrix), rather than freshwater cable bacteria, which form a separate genus (Candidatus Electronema) and contribute essential geochemical roles in freshwater sediments. Here, we characterize the electron transport characteristics of Ca. Electronema cable bacteria from Southern California freshwater sediments. Current-voltage measurements of intact cable filaments bridging interdigitated electrodes confirmed their persistent conductivity under a controlled atmosphere and the variable sensitivity of this conduction to air exposure. Electrostatic and conductive atomic force microscopies mapped out the characteristics of the cell envelope's nanofiber network, implicating it as the conductive pathway in a manner consistent with previous findings in marine cable bacteria. Four-probe measurements of microelectrodes addressing intact cables demonstrated nanoampere currents up to 200 μm lengths at modest driving voltages, allowing us to quantify the nanofiber conductivity at 0.1 S/cm for freshwater cable bacteria filaments under our measurement conditions. Such a high conductivity can support the remarkable sulfide-to-oxygen electrical currents mediated by cable bacteria in sediments. These measurements expand the knowledgebase of long-distance electron transport to the freshwater niche while shedding light on the underlying conductive network of cable bacteria.

A cytochrome bd repressed by a MarR family regulator confers resistance to metals, nitric oxide, sulfide, and cyanide in Chromobacterium violaceum.

The terminal oxidases of bacterial respiratory chains rely on heme-copper (heme-copper oxidases) or heme (cytochrome bd ) to catalyze reduction of molecular oxygen to water. Chromobacterium violaceum is a facultative anaerobic bacterium that uses oxygen and other electron acceptors for respiration under conditions of varying oxygen availability. The C. violaceum genome encodes multiple respiratory terminal oxidases, but their role and regulation remain unexplored. Here, we demonstrate that CioAB, the single cytochrome bd from C. violaceum , protects this bacterium against multiple stressors that are inhibitors of heme-copper oxidases, including nitric oxide, sulfide, and cyanide. CioAB also confers C. violaceum resistance to iron, zinc, and hydrogen peroxide. This cytochrome bd is encoded by the cioRAB operon, which is under direct repression by the MarR-type regulator CioR. In addition, the cioRAB operon responds to quorum sensing and to cyanide, suggesting a protective mechanism of increasing CioAB in the setting of high endogenous cyanide production.

Point-Defect Segregation and Space-Charge Potentials at the Σ5(310)[001] Grain Boundary in Ceria

The atomistic structure and point-defect thermodynamics of the model Σ5(310)[001] grain boundary in CeO2 were explored with atomistic simulations. An interface with a double-diamond-shaped structural repeat unit was found to have the lowest energy. Segregation energies were calculated for oxygen vacancies, electron polarons, gadolinium and scandium acceptor cations, and tantalum donor cations. These energies deviate strongly from their bulk values over the same length scale, thus indicating a structural grain-boundary width of approximately 1.5 nm. However, an analysis revealed no unambiguous correlation between segregation energies and local structural descriptors, such as interatomic distance or coordination number. From the segregation energies, the grain-boundary space-charge potential in Gouy–Chapman and restricted-equilibrium regimes was calculated as a function of temperature for dilute solutions of (i) oxygen vacancies and acceptor cations and (ii) electron polarons and donor cations. For the latter, the space-charge potential is predicted to change from negative to positive in the restricted-equilibrium regime. For the former, the calculation of the space-charge potential from atomistic segregation energies is shown to require the inclusion of the segregation energies for acceptor cations. Nevertheless, the space-charge potential in the restricted-equilibrium regime can be described well with an empirical model employing a single effective oxygen-vacancy segregation energy.

Uncovering the role of oxygen on organic carbon cycling: insights from a continuous culture study with a facultative anaerobic bacterioplankton species (Shewanella baltica)

Deoxygenation is tied to organic carbon (Corg) supply and utilization in marine systems. Under oxygen-depletion, bacteria maintain Corg respiration using alternative electron acceptors such as nitrate. Since anaerobic respiration’s energy yield is lower, Corg remineralization may be reduced and its residence time increased. We investigated the influence of oxygen and alternative electron acceptors’ availability on Corg cycling by heterotrophic bacteria during a continuous culture experiment with Shewanella baltica, a facultative anaerobic γ-Proteobacteria in the Baltic Sea. We tested six different oxygen levels, from suboxic (<5 µmol L-1) to fully oxic conditions, using a brackish (salinity=14 g L-1) media supplied with high (HighN) or low (LowN) inorganic nitrogen concentrations relative to glucose as labile Corg source. Our results show that suboxia limited DOC (glucose) uptake and cell growth only under LowN, while higher availability of alternative electron acceptors seemingly compensated oxygen limitation under HighN. N-loss was observed under suboxia in both nitrogen treatments. Under HighN, N-loss was highest and a C:N loss ratio of ~2.0 indicated that Corg was remineralized via denitrification. Under LowN, the C:N loss ratio under suboxia was higher (~5.5), suggesting the dominance of other anaerobic respiration pathways, such as dissimilatory nitrate reduction to ammonium (DNRA). Bacterial growth efficiency was independent of oxygen concentration but higher under LowN (34 ± 3.0%) than HighN (26 ± 1.6%). Oxygen concentration also affected dissolved organic matter (DOM) cycling. Under oxic conditions, the release of dissolved combined carbohydrates was enhanced, and the amino acid-based degradation index (DI) pointed to more diagenetically altered DOM. Our results suggest bacterial Corg uptake in low-oxygen systems dominated by S. baltica can be limited by oxygen but compensated by high nitrate availability. Hence, suboxia diminishes Corg remineralisation only when alternative electron acceptors are lacking. Under high nitrate:Corg supply, denitrification leads to a higher N:C loss ratio, potentially counteracting eutrophication in the long run. Low nitrate:Corg supply may favour other anaerobic respiration pathways like DNRA, which sustains labile nitrogen in the system, potentially intensifying the cycle of eutrophication. Going forward, it will be crucial to establish the validity of our findings for S. baltica in natural systems with diverse organic substrates and microbial consortia.

Relayed Heteroatom Group Transfer: A Structural Reorganization between Bisthioester and Triaminophosphine to α,α-Disulfenylamide.

Simultaneous multiple displacements of organic molecules can lead to a large structural reconstruction with increased complexity that would be difficult to access otherwise. Whereas double displacement such as olefin metathesis is well-established, higher-order versions remain much more challenging, because of their intrinsic thermodynamic disadvantages. Here, we describe a newly discovered relayed heteroatom group transfer process between bisthioesters and triaminophosphines as an unusual example of a formal triple displacement. Through the oxygen/nitrogen exchange between the two simple starting materials, in addition to the 1,2-sulfur migration of a putative carbene intermediate, an organized relocation of the O/S/N groups proceeded to give a variety of α,α-disulfenylamides with excellent efficiency under ambient conditions. The experimental and computational mechanistic studies revealed the sequence of the relayed group shifts via an α,α-disulfenyl phosphonium enolate intermediate as well as the dual role of triaminophosphine as both an oxygen acceptor and a nitrogen donor.

Effects of Graphene Oxide (GO) and Reduced Graphene Oxide (rGO) on Green-Emitting Conjugated Copolymer's Optical and Laser Properties Using Simulation and Experimental Studies.

The properties of a conjugated copolymer (CP), poly[(9,9-Dioctyl-2,7-divinylenefluorenylene)-alt-co-(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene) (PDVF-co-MEH-PV), were investigated in the presence of graphene oxide (GO) and reduced graphene oxide (rGO) using absorption, fluorescence, laser, and time-resolved spectroscopy. CPs are usually dissolved in low-polar solvents. Although GO does not dissolve well, rGO and PDVF-co-MEH-PV dissolve in chloroform due to their oxygen acceptor sites. Hence, we studied rGO/PDVF-co-MEH-PV (CP/rGO), performing all experiments and simulations in chloroform. We performed simulations on PDVF-co-MEH-PV, approximate GO, and rGO using time-dependent density-functional theory calculations to comprehend the molecular dynamics and interactions at the molecular level. The simulation polymer used a tail-truncated oligomer model with up to three monomer units. The simulation and experimental results were in agreement. Further, the PDVF-co-MEH-PV exhibited fluorescence, laser quenching, rGO-mediated laser blinking, and spectral broadening effects when GO and rGO concentrations increased. The experimental and simulation results were compared to provide a plausible mechanism of interaction between PDVF-co-MEH-PV and rGO. We observed that for lower concentrations of rGO, the interaction did not considerably decrease the amplified spontaneous emissions of PDVF-co-MEH-PV. However, the fluorescence of PDVF-co-MEH-PV was considerably quenched at higher concentrations of rGO. These results could be helpful for future applications, such as in sensors, solar cells, and optoelectronic device design. To demonstrate the sensor capability of these composites, a paper-based sensor was designed to detect ethanol and nitrotoluene. An instrumentation setup was proposed that is cheap, reusable, and multifunctional.

The electronic structure regulation improving xylene gas sensing properties in p-type Zn-doped α-Fe2O3 nanoparticles

Xylene is a highly carcinogenic inert gas, and achieving highly selective detection toward xylene gas is crucial for environmental protection and physical health. Herein, α-Fe2O3 nanoparticles doped with different Zn contents (ZF-0, ZF-1, ZF-2 and ZF-3) have been prepared through a feasible solvothermal and subsequent annealing treatment. The successful doping of Zn has been confirmed through EDS, XPS and XRD characterizations. After Zn doping, the baseline resistance in air reduces, the band gap and specific surface area decrease, but oxygen vacancy defects increase for α-Fe2O3 nanoparticles. When applied as gas sensors, all as-prepared α-Fe2O3 samples show typical p-type semiconductor gas sensing behaviors. Especially, the ZF-2 sample with appropriate amount of Zn doping exhibits an excellent xylene gas sensing selectivity. Meanwhile, the ZF-2 sensor shows a high response, fast response/recovery speed, well stability and repeatability and a detection limit of 5 ppm at 240 °C. The acceptor level and oxygen vacancy defects in ZF-2 nanoparticles promote the catalytic oxidation of xylene gas by p-type Zn-doped α-Fe2O3 oxide semiconductors, thereby resulting in better xylene gas sensing performance.

Enhanced dopant incorporation into SnO2 thin films based on dual source spray pyrolysis deposition process

Recently, SnO2 has attracted much attention for optoelectronic applications in infrared (IR) spectral ranges due to its high transparency in the ultraviolet to IR wavelength spectral range and high electrical conductivity. The transition metal-doped SnO2 based on the ultrasonic-assisted spray pyrolysis deposition (SPD) method has been widely used for various optoelectronic applications. However, the SPD process has suffered from inefficient doping of foreign elements due to difficulties in controlling the single precursor source solutions and complicated solution dynamics. To overcome these problems, the co-SPD process supplying the host and dopant solutions separately was suggested for the deposition of the Zn-doped SnO2 thin films. The Zn-doped SnO2 thin films deposited by co-SPD showed insulating electrical properties due to the efficient incorporation of the Zn element as an oxygen vacancy scavenger and acceptor to annihilate the free charge carriers. Also, the Zn-doped SnO2 films showed an IR transmittance of over 80 %, maintained at a temperature of up to 500 ℃. Thus, the co-SPD process can be a promising approach to achieve highly doped oxide films with high IR transmittance even at elevated temperatures.

Bioremediation of contaminated soil and groundwater by in situ biostimulation.

Bioremediation by in situ biostimulation is an attractive alternative to excavation of contaminated soil. Many in situ remediation methods have been tested with some success; however, due to highly variable results in realistic field conditions, they have not been implemented as widely as they might deserve. To ensure success, methods should be validated under site-analogous conditions before full scale use, which requires expertise and local knowledge by the implementers. The focus here is on indigenous microbial degraders and evaluation of their performance. Identifying and removing biodegradation bottlenecks for degradation of organic pollutants is essential. Limiting factors commonly include: lack of oxygen or alternative electron acceptors, low temperature, and lack of essential nutrients. Additional factors: the bioavailability of the contaminating compound, pH, distribution of the contaminant, and soil structure and moisture, and in some cases, lack of degradation potential which may be amended with bioaugmentation. Methods to remove these bottlenecks are discussed. Implementers should also be prepared to combine methods or use them in sequence. Chemical/physical means may be used to enhance biostimulation. The review also suggests tools for assessing sustainability, life cycle assessment, and risk assessment. To help entrepreneurs, decision makers, and methods developers in the future, we suggest founding a database for otherwise seldom reported unsuccessful interventions, as well as the potential for artificial intelligence (AI) to assist in site evaluation and decision-making.

Molecular design and systematic optimization of a halogen-bonding system between the asthma interleukin-5 receptor and its cyclic peptide ligand.

Human interleukin-5 (IL-5) functions as an important pro-inflammatory factor by binding to its specific receptor, IL-5Rα, which has been implicated in the pathogenesis of asthma. Previously, a disulfide-bonded cyclic peptide AF17121 obtained from random library screening and sequence variation was found to competitively disrupt the cognate IL-5Rα/IL-5 interaction with moderate potency. In this study, the crystal complex of IL-5Rα with AF17121 was investigated at structural and energetic levels. It is revealed that the side-chain indole moiety of the AF17121 Trp5 residue is a potential site for a stem putative halogen bond (X-bond) with IL-5Rα, which is just located within the key 3 EXXR6 motif region recognized specifically by IL-5Rα. We systematically examined four halogen substitution types at five positions of the indole moiety; QM/MM calculations theoretically unraveled that only halogenations at 5 and 6 positions can form effective X-bonds with the side-chain hydroxyl oxygen of the IL-5Rα Thr21 residue and the backbone carbonyl oxygen of Ala66 residue, respectively. Binding assays observed that I-substitution at the 5 position and Br-substitution at the 6 position can result in two potent halogenated peptides, [5I]AF17121 and [6Br]AF17121, which are improved by 1.6-fold and 3.5-fold relative to the native AF17121, respectively. 5I/6Br-double substitution, resulting in [5I/6Br]AF17121, can further enhance the peptide affinity by 7.5-fold. Structural analysis revealed that the X-bond stemming from 6Br-substitution is also involved in an orthogonal interaction system with a H-bond; they share a common backbone carbonyl oxygen acceptor of IL-5Rα Ala66 residue and exhibit a significant synergistic effect between them.

Cooperativity and topological hydrogen bonding in aromatic diol complexes

AbstractComplexes of three aromatic diols, catechol, naphthalene‐1,8‐diol, and fluorene‐4,5‐diol, with a series of hydrogen bond acceptors (HBAs) that have oxygen, nitrogen, and sulfur acceptor atoms, have been studied by density functional theory (DFT) at the B3LYP/6‐311+G(d,p) level. Binding energies, geometries, infrared spectroscopic (IR) frequencies, nuclear magnetic resonance (NMR) shifts, and measures of the electron density distribution from the Quantum Theory of Atoms in Molecules (QTAIM) are evaluated and compared with data for the corresponding monohydroxy compounds (monols), phenol, naphth‐1‐ol, and fluorene‐4‐ol, in order to assess the importance of cooperativity between intramolecular and intermolecular hydrogen bonding. All measures for all complexes show positive cooperativity whereby both the intermolecular and intramolecular hydrogen bonds are strengthened upon complexation. Cooperativity is weak for catechol and strong for the other two diols and, for all diols, increases with the hydrogen bond basicity of the acceptor. Correlations of IR and NMR metrics against binding energies for a single HBA and all six monols and diols are excellent, but attempts to correlate the same metrics for all HBAs and a single donor are frustrated by differences in intermolecular hydrogen bonding, depending notably on the identity of the acceptor atom in the HBA. Atom–atom interaction energies, calculated by the Interacting Quantum Atoms approach, are used to discuss the covalency of both types of hydrogen bond.

Improved Energy Storage Density and Efficiency of Nd and Mn Co-Doped Ba0.7Sr0.3TiO3 Ceramic Capacitors Via Defect Dipole Engineering.

In this paper, we investigate the structural, microstructural, dielectric, and energy storage properties of Nd and Mn co-doped Ba0.7Sr0.3TiO3 [(Ba0.7Sr0.3)1-xNdxTi1-yMnyO3 (BSNTM) ceramics (x = 0, 0.005, and y = 0, 0.0025, 0.005, and 0.01)] via a defect dipole engineering method. The complex defect dipoles (MnTi"-VO∙∙)∙ and (MnTi"-VO∙∙) between acceptor ions and oxygen vacancies capture electrons, enhancing the breakdown electric field and energy storage performances. XRD, Raman, spectroscopy, XPS, and microscopic investigations of BSNTM ceramics revealed the formation of a tetragonal phase, oxygen vacancies, and a reduction in grain size with Mn dopant. The BSNTM ceramics with x = 0.005 and y = 0 exhibit a relative dielectric constant of 2058 and a loss tangent of 0.026 at 1 kHz. These values gradually decreased to 1876 and 0.019 for x = 0.005 and y = 0.01 due to the Mn2+ ions at the Ti4+- site, which facilitates the formation of oxygen vacancies, and prevents a decrease in Ti4+. In addition, the defect dipoles act as a driving force for depolarization to tailor the domain formation energy and domain wall energy, which provides a high difference between the maximum polarization of Pmax and remnant polarization of Pr (ΔP = 10.39 µC/cm2). Moreover, the complex defect dipoles with optimum oxygen vacancies in BSNTM ceramics can provide not only a high ΔP but also reduce grain size, which together improve the breakdown strength from 60.4 to 110.6 kV/cm, giving rise to a high energy storage density of 0.41 J/cm3 and high efficiency of 84.6% for x = 0.005 and y = 0.01. These findings demonstrate that defect dipole engineering is an effective method to enhance the energy storage performance of dielectrics for capacitor applications.

Deoxygenation of Oxiranes by λ3 σ3 -Phosphorus Reagents: A Computational, Mechanistic, and Stereochemical Study.

The deoxygenation of parent and substituted oxiranes by λ3 σ3 -phosphorus reagents has been explored in detail, therefore unveiling mechanistic aspects as well as regio- and stereochemical consequences. Attack to a ring C atom is almost always preferred over one-step deoxygenation by direct P-to-O attack. In most cases a carbene transfer occurs as first step, leading to a phosphorane and a carbonyl unit that thereafter react in the usual Wittig fashion via the corresponding λ5 σ5 -1,2-oxaphosphetane intermediate. Betaines rarely constitute true minima after the first C-attack to oxiranes, at least in the gas-phase. Use of the heavier derivatives AsMe3 and SbMe3 as oxirane deoxygenating reagents was also mechanistically studied. The thermodynamic tendency of λ3 σ3 -phosphorus reagents to act as oxygen (O-attack) or carbene acceptors (C-attack) was theoretically studied by means of the thermodynamic oxygen-transfer potential (TOP) and the newly defined thermodynamic carbene-transfer potential (TCP) parameters, that were explored in a wider context together with many other acceptor centres.

N-X⋅⋅⋅O-N Halogen Bonds in Complexes of N-Haloimides and Pyridine-N-oxides: A Large Data Set Study.

N-X⋅⋅⋅- O-N+ halogen-bonded systems formed by 27 pyridine N-oxides (PyNOs) as halogen-bond (XB) acceptors and two N-halosuccinimides, two N-halophthalimides, and two N-halosaccharins as XB donors are studied in silico, in solution, and in the solid state. This large set of data (132 DFT optimized structures, 75 crystal structures, and 168 1 H NMR titrations) provides a unique view to structural and bonding properties. In the computational part, a simple electrostatic model (SiElMo) for predicting XB energies using only the properties of halogen donors and oxygen acceptors is developed. The SiElMo energies are in perfect accord with energies calculated from XB complexes optimized with two high-level DFT approaches. Data from in silico bond energies and single-crystal X-ray structures correlate; however, data from solution do not. The polydentate bonding characteristic of the PyNOs' oxygen atom in solution, as revealed by solid-state structures, is attributed to the lack of correlation between DFT/solid-state and solution data. XB strength is only slightly affected by the PyNO oxygen properties [(atomic charge (Q), ionization energy (Is,min ) and local negative minima (Vs,min )], as the σ-hole (Vs,max ) of the donor halogen is the key determinant leading to the sequence N-halosaccharin>N-halosuccinimide>N-halophthalimide on the XB strength.

N−X⋅⋅⋅O−N Halogen Bonds in Complexes of N‐Haloimides and Pyridine‐N‐oxides: A Large Data Set Study

AbstractN−X⋅⋅⋅−O−N+ halogen‐bonded systems formed by 27 pyridine N‐oxides (PyNOs) as halogen‐bond (XB) acceptors and two N‐halosuccinimides, two N‐halophthalimides, and two N‐halosaccharins as XB donors are studied in silico, in solution, and in the solid state. This large set of data (132 DFT optimized structures, 75 crystal structures, and 168 1H NMR titrations) provides a unique view to structural and bonding properties. In the computational part, a simple electrostatic model (SiElMo) for predicting XB energies using only the properties of halogen donors and oxygen acceptors is developed. The SiElMo energies are in perfect accord with energies calculated from XB complexes optimized with two high‐level DFT approaches. Data from in silico bond energies and single‐crystal X‐ray structures correlate; however, data from solution do not. The polydentate bonding characteristic of the PyNOs’ oxygen atom in solution, as revealed by solid‐state structures, is attributed to the lack of correlation between DFT/solid‐state and solution data. XB strength is only slightly affected by the PyNO oxygen properties [(atomic charge (Q), ionization energy (Is,min) and local negative minima (Vs,min)], as the σ‐hole (Vs,max) of the donor halogen is the key determinant leading to the sequence N‐halosaccharin>N‐halosuccinimide>N‐halophthalimide on the XB strength.

Evolution of pH, redox potential and solute concentrations in soil and drainage water at a cultivated acid sulfate soil profile

Land drainage lowers the soil water table, which triggers enhanced oxidation of iron sulfide minerals in acid sulfate soils, causing acidification of fields and posing environmental hazards to aquatic ecosystems. The objective of this study was to develop a model for investigating the effects of oxidation of iron sulfide minerals and the cation exchange capacity (CEC) on the long-term evolution of pH, redox potential and solute concentrations in soil water and drain discharge. Two electron acceptors (oxygen and ferric iron) were included in the model. The model was implemented in the HP1 modeling platform (coupled HYDRUS-1D and PHREEQC-3) and applied to an acid sulfate soil profile of an agricultural field in Finland. The geochemical part of the model was tested against field observations. A comparison of different model versions showed that CEC had an essential role in mimicking the observed pH profile of soil. The drain discharge water quality was similar in the model versions both with and without CEC, but the buffering effect of CEC could be seen as lower iron concentrations. The oxidation of metastable iron sulfide minerals was three times faster than the oxidation of pyrite. Descriptions for the oxidation of both two minerals and for CEC were required to conduct long-term simulations that reproduce the observed geochemical state of a drained agricultural field. The HP1 modeling platform facilitated the testing of alternative chemical transformation processes of an AS soil profile in response to increased drainage efficiency after subsurface drainage installation.

Redox control of tumor cell apoptosis during hypoxia

Currently, close attention is paid to studies aimed at searching for redox-sensitive targets for the regulation of tumor cell death. Tumor growth is characterized by impaired cell proliferation, differentiation, and apoptosis against the background of oxidative stress. Hypoxia contributes to the formation of mitochondrial dysfunction and acts as an additional factor that exacerbates oxidative stress in the tumor cell. Reactive oxygen species are general damaging factors, however, they can act as modulators of processes such as reception, intracellular signaling, proliferation, apoptosis, while taking part in the functioning of the cell redox system and contributing to the oxidative modification of macromolecules. One of the possible reasons for the activation of the production of reactive oxygen species is the low content of O2 in the cell, the final electron acceptor to ensure the functioning of the enzymes of the mitochondrial respiratory chain. The glutathione system makes a significant contribution to maintaining the balance between prooxidants and antioxidants in the cell. The role of this system is justified by the reduction potential of glutathione, which, acting as an acceptor of hydroxyl ions and singlet oxygen, significantly reduces the cytotoxic and damaging effects of reactive oxygen species. At the same time, it serves as a coenzyme for glutathione-dependent enzymes, which play a leading role not only in providing antioxidant processes, but also in maintaining the thiol disulfide balance. Hypoxia, which acts as a factor in the activation of free radical oxidation against the background of proliferation and apoptosis dysregulation, contributes to the formation of resistance of tumor cells to chemotherapeutic effects. In light of this, the importance of studying the redox-dependent mechanisms involved in the regulation and implementation of tumor cell death under insufficient oxygen supply becomes obvious, which is necessary for the development of personalized antitumor therapy. The article presents a review of modern literature, including the results of our own research, on the role of the thiol disulfide system and oxidatively modified proteins in the redox regulation of proliferation and apoptotic death of tumor cells, including under hypoxic conditions.

In vivo noninvasive mitochondrial redox assessment of the optic nerve head to predict disease.

Eye diseases are diagnosed by visualizing often irreversible structural changes occurring late in disease progression, such as retinal ganglion cell loss in glaucoma. The retina and optic nerve head have high mitochondrial energy need. Early mitochondrial/energetics dysfunction may predict vulnerability to permanent structural changes. In the in vivo murine eye, we used light-based resonance Raman spectroscopy (RRS) to assess noninvasively the redox states of mitochondria and hemoglobin which reflect availability of electron donors (fuel) and acceptors (oxygen). As proof of principle, we demonstrated that the mitochondrial redox state at the optic nerve head correlates with later retinal ganglion loss after acute intraocular pressure (IOP) elevation. This technology can potentially map the metabolic health of eye tissue in vivo complementary to optical coherence tomography, defining structural changes. Early detection (and normalization) of mitochondrial dysfunction before irreversible damage could lead to prevention of permanent neural loss.