Higher Oxidative Levels Research Articles

Surface Acoustic Wave Nebulization–Mass Spectrometry as a New Tool to Investigate the Water Sensitivity Behavior of 20th Century Oil Paints

The sensitive surfaces of many unvarnished 20th century oil paintings are of great concern for conservators and collection keepers. They may show degradation problems such as paint delamination, dripping, and soft and sticky paint and pose challenges for cleaning due to solvent sensitivity. We report for the first time the use of an innovative ambient ionization technique, surface acoustic wave nebulization-mass spectrometry (SAWN-MS), for the identification and characterization of fatty acids, dicarboxylic species and glycerides in water-sensitive modern oil paints. The composition of 10 relevant Winsor and Newton 1964-1965 paint swatches that present different degrees of water sensitivity and two paint samples from a painting by the British artist Francis Bacon were studied. Principal component analysis was used for SAWN-MS data classification. Electrospray ionization (ESI)-MS was used as control method, specifically to compare the obtained ratios of markers of interest by the two ionization techniques. The results obtained by both ESI-MS and SAWN-MS are correlated and discussed in a broader context including the information on the oil media obtained by gas chromatography (GC-MS) and also on the inorganic materials and salts characterized using a combination of methods in previous reports on samples from the same manufacturer. SAWN-MS was found to be a suitable tool for the determination of soluble organic constituents present in the paints. The method provides an indication of the level of oxidation and hydrolysis of the paint film by monitoring specific markers such as free palmitic and stearic acids, azelaic acid, monoacylglycerols, and diacylglycerols. The data showed that a higher level of water sensitivity coupled with a high level of oxidation and hydrolysis is linked to higher dicarboxylic acid, diacyl- and triacylglyceride content and lower levels of short chain fatty acids. The data obtained by SAWN-MS provided a good correlation between the monitored species and the degree of water sensitivity.

Genetically raised serum bilirubin levels and lung cancer: a cohort study and Mendelian randomisation using UK Biobank

BackgroundModerately raised serum bilirubin levels are associated with lower rates of lung cancer, particularly among smokers. It is not known whether these relationships reflect antioxidant properties or residual confounding.ObjectiveThis study...

Effect of oxidation degree on the thermal properties of graphene oxide

The introduction of graphene oxide into both metals and polymers has yielded materials with enhanced thermal properties. Of particular interest is functionalized graphene oxide containing substantially heterogeneously distributed functional groups. The thermal properties of graphene oxide were investigated using non-equilibrium molecular dynamics to understand mechanism of thermal transport at the nanoscale. The mechanism of phonon transport in the functionalized graphene sheet was discussed, and the structure factors limiting phonon transport were determined. The results indicated that the oxidation level influences the thermal conductivity greatly. There is a need to reduce the oxidation level in order to enhance phonon transport and reduce phonon scattering in the functionalized graphene sheet. Phonon transport in the functionalized graphene sheet at a high oxidation level is governed by the phonon mean free path associated with phonon-defect scattering. Oxygen-containing functional groups adversely influence the thermal properties due to enhanced phonon-scattering arising from the increased number of phonon-scattering centers. The intrinsic thermal conductivity of about 2480W/(mK) at room temperature agrees with existing data on single layer pristine graphene. At room temperature, the intrinsic thermal conductivity is around 72W/(mK) at an oxidation level of 0.35 and around 670W/(mK) at an oxidation level of 0.05. The phonon mean free path is limited mainly by interior defects and decreases with increasing the oxidation level due to enhanced phonon-defect scattering.

Investigation of the usability of nitric acid electrolyte in graphene production by electrochemical method

Electrochemical exfoliation method, which is one of the methods of producing graphene, is a suitable technique for the mass production of graphene in the industrial sense. However, the correct selection of electrochemical process inputs (electrolyte, applied voltage, etc.) is very important for graphene formation. Otherwise, thick fragmented graphites are formed. In this study, a method for producing ultrathin layer graphene using dilute nitric acid has been presented. The properties of the produced graphene were characterized. Structural analysis was done with X-Ray diffraction device, Raman Spectroscopy, energy dispersive x-ray spectrometry. The morphological structure of the surface was performed using scanning electron microscopy. The data obtaining were discussed together with the literature and the results were evaluated. In addition to being a good electrolyte in the production of graphene, nitric acid is determined to be a good candidate for the production of graphene oxide in one step with this method with its high oxidation level.

Melatonin maintains the function of the blood redox system at combined ethanol-induced toxicity and subclinical inflammation in mice

BackgroundThe goal of this study was to assess the effect of melatonin on blood redox systems in mice simultaneously exposed to ethanol and low-dose lipopolysaccharide (LPS).MethodsOxidative stress parameters were assessed in eight groups: untreated control, melatonin (10 mg kg−1, 10 days), LPS (injected once intraperitoneally at a dose of 150 μg per mouse), LPS with previous melatonin treatment, acute ethanol-induced stress (AES, 0.75 g kg−1 per day, 10 days), AES with previous melatonin treatment, LPS- and AES-induced toxicity, and melatonin treatment.ResultsBoth ethanol and LPS induced oxidative stress. The combination of these two factors was even more toxic to the organism. Melatonin stabilized erythrocyte membranes and decreased the high level of free radical oxidation at the initial and final stages. Furthermore, melatonin limited protein damage through maintenance in the functional ability of the blood redox system to counteract pathological conditions.ConclusionsMelatonin limited the negative effects associated with alcohol consumption and low-intensity inflammation.

Enzymatic hydrolysis of farmed Atlantic salmon by-products: Investigation of operational parameters on extracted oil yield and quality

Six operational parameters (fish part, antioxidant addition, water addition, enzyme species, enzyme concentration and hydrolysis time) were studied for their effect on yield and quality of enzymatically extracted oil from farmed Atlantic salmon by-products. The highest oil yield of 26.0% (93.6% recovery) was obtained from salmon viscera using 1% Flavourzyme for 2 h without addition of water or the antioxidant. Averagely, salmon viscera produced more oil compared to mixture of salmon heads and frames. However, viscera oil had higher levels of oxidation and hydrolysis, indicating inferior quality. The use of Alcalase resulted in the highest oil quality compared to Flavourzyme and SEBPro, due to less oil oxidation and free fatty acids in the alkaline environment using Alcalase (pH 8). The enzyme concentration studied (0.1 and 1%) didn’t have any significant effect on oil yield or oxidation. At 1% enzyme concentration, the oil extracted from 4 h hydrolysis had higher levels of oxidation but lower level of free fatty acids compared to the oil extracted from 2 h hydrolysis. Addition of water significantly decreased both oil yield and quality. The use of antioxidant (0.15%) didn’t affect oil yield but significantly inhibited oil oxidation.

Mycobacterium tuberculosis Calcium Pump CtpF Modulates the Autophagosome in an mTOR-Dependent Manner.

Calcium is a very important second messenger, whose concentration in various cellular compartments is under tight regulation. A disturbance in the levels of calcium in these compartments can play havoc in the cell, as it regulates various cellular processes by direct or indirect mechanisms. Here, we have investigated the functional importance of a calcium transporting P2A ATPase, CtpF of Mycobacterium tuberculosis (Mtb) in the pathogen's interaction with the host. Among its uncanny ways of dealing with the host with umpteen strategies for survival and persistence in humans, CtpF is identified as a new player. The levels of ctpF are upregulated in macrophage stresses like hypoxia, high nitric oxide levels and acidic pH. Using confocal microscopy and fluorimetry, we show that CtpF effluxes calcium in macrophages in early stages of Mtb infection. Downregulation of ctpF expression by conditional knockdown resulted in perturbation of host calcium levels and consequent decreased activation of mTOR. We present a mechanism how calcium efflux by the pathogen inhibits mTOR-dependent autophagy and enhances bacterial survival. Our work highlights how Mtb engages its metal efflux pumps to exploit host autophagic process for its proliferation.

Dissipation of pyridaphenthion by cyanobacteria: Insights into cellular degradation, detoxification and metabolic regulation

Excessive use of organophosphorus pesticides such as pyridaphenthion (PY) to constrain insects induced crop loss, results in soil and water sources contamination. Cyanobacteria are sensitive biological indicators and promising tools for bioremediation of soil and water pollutants. To understand PY toxicity, detoxification and degradation in cyanobacteria, we performed a comparative study in the two diazotrophic cyanobacteria; Anabaena laxa and Nostoc muscorum. They were exposed to mild (5 mg/L) and high (10 mg/L) concentrations of PY for 7 days. Compared to A. laxa, N. muscorum efficiently showed high PY accumulation and degradation to a safe environmentally product; 6-hydroxy-2-phenylpyridazin-3(2 H)-one. PY inhibited cell growth and reduced Chl a content and photosynthesis related enzymes (PEPC and RuBisCo) activities in both species, but to less extend in N. muscorum. It also induced oxidative damage, particularly in A. laxa, as indicated by high H2O2, lipid peroxidation and protein oxidation levels and increased NADPH oxidase enzyme activity. N. muscorum invested more in antioxidants induction, i.e., induced ascorbate and glutathione cycle, however, these antioxidants increments in A. laxa were less pronounced. Overall, this study provides more in-deep insights into the PY toxicity and the role of N. muscorum as a promising PY remediator.

Changes in Protein Fluorescence in a Lipid-Protein Co-oxidizing Oleogel.

High and low levels of lipid-induced protein oxidation (tuned by the addition of 0%-8.4% water) were investigated in oleogels, using excitation-emission matrix (EEM) fluorescence spectroscopy, coupled with a partial least-squares (PLS) regression and lipid hydroperoxide data. In high-level oxidation models, the intrinsic tryptophan fluorescence decreased and the emission maxima increased from 352.5 to 356.0 nm indicating the presence of protein modifications, which was further supported by size-exclusion chromatography. PLS recognized 3 latent components, with several excitation-emission points of interest. These apparent compounds include a region associated with radical mediated protein modifications (approximately 325 and 410 nm), lipid oxidation product adducts (approximately 350 nm and 420-425 nm), and malondialdehyde adducts (approximately 375 and 425 nm). The separate evaluation of these apparent compounds, at a 420 nm emission, indicated that lipid oxidation promotes protein lipid adduct fluorescence at high water levels, rather than radical mediated protein fluorescence.

Decorating sulfur and nitrogen co-doped graphene quantum dots on graphite felt as high-performance electrodes for vanadium redox flow batteries

This paper reports on decorating sulfur (S)/nitrogen (N) co-doped graphene quantum dots (S/N co-doped GQDs) on graphite felt as high-performance electrodes for vanadium redox flow batteries (VRFBs). The S/N co-doped GQDs are synthesized through an efficient infrared-assisted pyrolysis of glucose, urea, and ammonia sulfate at 280 °C. The S/N co-doped GQDs, having an average diameter of 6.2 nm, contain high oxidation, amidation, and sulfuration levels (45.8 (O/C), 22.7 (N/C), and 7.8 at.% (S/C), respectively). Electrochemical impedance spectroscopy is utilized to assess the overpotential distributions for VRFBs equipped with untreated GF and S/N co-doped GQDs/GF. With the aid of S/N co-doped GQDs, the catalytic activity, equivalent series resistance, durability, and voltage efficiency are substantially improved. The improved performance is attributed to the synergistic effect of GQDs containing O functionalities, lattice N atoms, and S dopants, facilitating surface catalytic activity and accelerating charge transfer across the anode/anolyte interface for the vanadium redox couples (V(II)/V(III)). Accordingly, hierarchical S/N co-doped GQD/GF electrode paves the pathway for engineering the electrodes’ nano-structure with improved catalytic activity and enhanced durability for redox flow batteries.

TrypOx, a Novel Eukaryotic Homolog of the Redox-Regulated Chaperone Hsp33 in Trypanosoma brucei.

ATP-independent chaperones are widespread across all domains of life and serve as the first line of defense during protein unfolding stresses. One of the known crucial chaperones for bacterial survival in a hostile environment (e.g., heat and oxidative stress) is the highly conserved, redox-regulated ATP-independent bacterial chaperone Hsp33. Using a bioinformatic analysis, we describe novel eukaryotic homologs of Hsp33 identified in eukaryotic pathogens belonging to the kinetoplastids, a family responsible for lethal human diseases such as Chagas disease as caused by Trypanosoma cruzi, African sleeping sickness caused by Trypanosoma brucei spp., and leishmaniasis pathologies delivered by various Leishmania species. During their pathogenic life cycle, kinetoplastids need to cope with elevated temperatures and oxidative stress, the same conditions which convert Hsp33 into a powerful chaperone in bacteria, thus preventing aggregation of a wide range of misfolded proteins. Here, we focused on a functional characterization of the Hsp33 homolog in one of the members of the kinetoplastid family, T. brucei, (Tb927.6.2630), which we have named TrypOx. RNAi silencing of TrypOx led to a significant decrease in the survival of T. brucei under mild oxidative stress conditions, implying a protective role of TrypOx during the Trypanosomes growth. We then adopted a proteomics-driven approach to investigate the role of TrypOx in defining the oxidative stress response. Depletion of TrypOx significantly altered the abundance of proteins mediating redox homeostasis, linking TrypOx with the antioxidant system. Using biochemical approaches, we identified the redox-switch domain of TrypOx, showing its modularity and oxidation-dependent structural plasticity. Kinetoplastid parasites such as T. brucei need to cope with high levels of oxidants produced by the innate immune system, such that parasite-specific antioxidant proteins like TrypOx – which are depleted in mammals – are highly promising candidates for drug targeting.

Oxidized Black Phosphorus Nanosheets as an Inorganic Antiresorptive Agent

Black phosphorus (BP) is a newly discovered two-dimensional material that has promising applications from bioelectronics to biomedicine. However, facile oxidation of BP leads to changes in surface ...

Physiological and Biochemical Traits in Korean Pine Somatic Embryogenesis

Korean pine broadleaf mixed forest is an important ecosystem for maintaining biodiversity in Northeast China. Korean pine is also an important species for the production of timber and nuts in the mountainous areas of Northeast China. In this study, we compared three types of Korean pine callus and found that embryogenic callus had high amounts of storage substances (protein, sugar and starch). Non-embryonic callus had high levels of polyphenols and polyphenol oxidation, while callus that lost somatic embryogenesis potential had lower levels of storage substances (protein, sugar and starch) and higher contents of peroxidase and catalase. These results indicate that high contents of storage substances (protein, sugar and starch), and low levels of polyphenols and polyphenol oxidase can be used as physiological markers of callus with somatic embryogenic potential. During the development process of Korean pine somatic embryos, fresh weight and dry weight gradually increased, while water content gradually decreased. Soluble protein, starch, soluble sugar and superoxide dismutase also increased during development, while peroxidase and catalase levels reduced over time. These results indicate that somatic embryogenesis involves energy storage, and antioxidant enzymes cooperate to regulate the occurrence and development of embryos. These results provide physiological markers for identification of embryogenic callus with somatic embryogenesis, to evaluate callus suitable for somatic embryogenesis, and provide basis for further research on the molecular mechanisms of somatic embryogenesis.

Ozone (O3) ambient levels as a secondary airborne precursor in Fahaheel urban area, the State of Kuwait

AbstractTwo years of continuous monitoring data over two time‐spans (2004–2005 and 2014–2015) were used to investigate the relationship between ozone (O3) and nitrogen oxides (NOX ≈ NO + NO2) in Fahaheel urban area (Kuwait). Their relationship was used to understand their chemical reactions and the NO2 and O3 concentration ratio to gain an insight into the sources of total atmospheric oxides (OX = O3 + NO2) levels. A Chemical Mass Balance (CMB) model was developed to detect likely point sources around the monitoring station and quantify their contribution to the overall air pollution load. Hourly diurnal variations in O3 ground level concentrations during weekends showed a slight increase in O3 levels. In addition, it was observed that overall hourly average O3 concentration reached higher levels during weekdays and weekends in 2004–2005 compared to 2014–2015. The concentration of photochemical oxidants (e.g., O3 and NO2) can be decreased by controlling the emissions of their precursors; NOX and VOCs. The net effect of NOX emissions on O3 concentrations was negative with a weak exponential decline correlation between NOX and O3, indicating Fahaheel urban area's VOC‐sensitive characteristics. For all years considered, the slopes of the linear OX–NOX relationships were higher during daytime compared to night‐time, showing that NO2 oxidations were dominant during daytime and that O3 net production was high. The study also showed the high NOX oxidation level and the possible presence of O3 net production. The slopes during night‐time indicated that NO2 consumption exceeded its formation rate. During day and night‐time, the NO2/NOX ratio was found to decline significantly as newly emitted NOX increased, supporting the area's VOC‐sensitive nature. By setting up a CMB model around the Fahaheel receptor point, it was revealed that downstream petroleum facilities have been the major contributor to pollutants environmental load over the years.

The effect of Cr additions and oxidation on densification, microstructure, phase constituents and mechanical properties of TiAlCr alloys produced by SPS

Ternary Ti-47.5Al-(1–3)Cr (at. %) and reference quaternary Ti-48Al-2Cr-2Nb (at. %) titanium aluminide alloys were processed from elemental powders utilizing mechanical milling, mechanical alloying and spark plasma sintering. The effect of Cr additions and oxidation on the densification behavior, microstructure, phase constituents and mechanical properties of the sintered alloys were investigated. The results point out that Cr additions and the presence of O play a significant role on the densification process i.e., compaction rates and sintering temperatures of the alloys. The microstructure and phase constituents of the alloys were studied based on historical experimental and theoretical data. Furthermore, the compression properties and fracture morphologies at experimental temperatures were found to be determined by a combination of response to densification, microstructural and phase evolutions effects as opposed to composition only. High additions of Cr coupled with the high level of oxidation impaired the compression properties of the ternary alloys, resulting in a 9% decrease in peak stress at higher testing temperatures. At these temperatures, the quaternary alloy showed good compression properties compared to the ternary alloys.

Oxidative Stress Induced by Loss of Superoxide Dismutases Leads to Activation of No‐Go Decay

Reactive oxygen species (ROS) are known to cause oxidative damage in the cell and have been connected to many neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and cancer. Superoxide dismutases (SODs) are a group of enzymes that act to prevent oxidative damage from ROS by converting O2− to H2O2. In Saccharomyces cerevisiae, there are two SOD proteins that are expressed, each of which is conserved in humans. Sod1p is a cytoplasmic Cu/Zn coordinated enzyme, whereas Sod2p coordinates Mn2+ and localizes to mitochondria. Although there is significant data showing that loss of SOD proteins allows for high levels of intracellular oxidation, it is unknown what effects that would have on the translating pool of mRNA. Current work has revealed that strains lacking Sod1p have a moderate decrease in general translation and an increase in P‐body assembly. Furthermore, this reduction in translation is likely due to the formation of 8‐oxo(G) bases in mRNA, which can cause ribosome stalls leading to the subsequent activation of the No‐Go quality control pathway. No‐Go decay is mediated by the proteins Dom34p and Hbs1p, which act together to remove stalled ribosomes and promote endonucleolytic cleavage of the mRNA at the stall site. The 3′ fragment of mRNA is then localized to P‐bodies to be degraded 5′ to 3′ by Xrn1p, whereas the 5′ fragment is degraded by the cytoplasmic exosome.Sod2p performs a similar role to Sod1p, as it also converts O2− to H2O2, and plays an important role in preventing the formation of strong oxidant peroxynitrate (ONOO−). Given that it localizes to mitochondria, a loss of Sod2p would result in higher levels of mitochondrially derived ROS. To determine the effect of mitochondrially derived ROS on the translating pool of mRNA, both general translation and P‐body assembly will be analyzed in strains lacking Sod2p. If general translation is reduced and P‐body assembly is increased, then it will be ascertained whether No‐Go Decay is being upregulated in the absence of Sod2p. To perform this analysis, double mutant strains lack both Sod2p and No‐Go Decay will be created and further analyzed for general translational control and P‐body assembly.

Long-Term Adverse Effects of Oxidative Stress on Rat Epididymis and Spermatozoa.

Oxidative stress is a common culprit of several conditions associated with male fertility. High levels of reactive oxygen species (ROS) promote impairment of sperm quality mainly by decreasing motility and increasing the levels of DNA oxidation. Oxidative stress is a common feature of environmental pollutants, chemotherapy and other chemicals, smoke, toxins, radiation, and diseases that can have negative effects on fertility. Peroxiredoxins (PRDXs) are antioxidant enzymes associated with the protection of mammalian spermatozoa against oxidative stress and the regulation of sperm viability and capacitation. In the present study, we aimed to determine the long-term effects of oxidative stress in the testis, epididymis and spermatozoa using the rat model. Adult male rats were treated with tert-butyl hydroperoxide (t-BHP) or saline (control group), and reproductive organs and spermatozoa were collected at 3, 6, and 9 weeks after the end of treatment. We determined sperm DNA oxidation and motility, and levels of lipid peroxidation and protein expression of antioxidant enzymes in epididymis and testis. We observed that cauda epididymal spermatozoa displayed low motility and high DNA oxidation levels at all times. Lipid peroxidation was higher in caput and cauda epididymis of treated rats at 3 and 6 weeks but was similar to control levels at 9 weeks. PRDX6 was upregulated in the epididymis due to t-BHP; PRDX1 and catalase, although not significant, followed similar trend of increase. Testis of treated rats did not show signs of oxidative stress nor upregulation of antioxidant enzymes. We concluded that t-BHP-dependent oxidative stress promoted long-term changes in the epididymis and maturing spermatozoa that result in the impairment of sperm quality.

Effects of µ-calpain oxidation on Coregonus peled myofibrillar protein degradation in vitro.

The aim of this study was to evaluate the effect of µ-calpain oxidation on Coregonus peled myofibrillar protein degradation. In the present study, a hydroxyl radical oxidation system was selected to investigate oxidative modification on µ-calpain activity and its degradation on C. peled myofibrillar protein. When subjected to oxidation, the carbonyl content of µ-calpain significantly increased with the increasing of oxidation levels, and oxidation modification promoted the µ-calpain activity. Incubation of C. peled myofibrillar protein with oxidized µ-calpain resulted in the enhanced degradation of myosin heavy chains, actin, and troponin T, but the degradation of desmin at higher levels of oxidation was slightly inhibited, based on sodium dodecyl sulfate polyacrylamide gel electrophoresis and western blotting. This study suggests that oxidation treatment of µ-calpain could accelerate myofibrillar proteolysis through regulating the enzyme activity during postmortem aging. PRACTICAL APPLICATION: Endogenous proteases, especially µ-calpain, are reported to be involved in fish softening during early postmortem storage, which is critical to muscle quality. The cysteine residues of proteins are particularly sensitive to oxidation. The investigation of the effect of oxidation on µ-calpain (a cysteine protease) activity allows for the monitoring of its role in the postmortem proteolysis of fish myofibrils and the associated softening of fish meat, in an attempt to minimize this softening.

Electrochemical sensing of mercury ions in electrolyte solutions by nitrogen-doped graphene quantum dot electrodes at ultralow concentrations

Electrochemical detection of mercury ions in aqueous solution was investigated at indium tin oxide (ITO) conducting glass electrode modified by nitrogen-doped graphene quantum dots (N-doped GQDs). The N-doped GQDs with an average particle size of 4.5 nm were synthesized through an infrared-assisted pyrolysis of citric acid and urea at 250 °C. The GQD sample contains high oxidation and amidation level, i.e., O/C and N/C atomic ratios: 37.6% and 30.7%, respectively. The electrochemical sensing toward Hg2+ ions was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Based on the CV and EIS analyses, both the reductive and oxidative peak currents as well as the equivalent series resistance demonstrate a decreasing trend with increased Hg2+ concentration. The detection limit of N-doped GQD/ITO electrodes toward Hg2+ ions reached 10 ppb with the accumulation time of 32 s. The GQD/ITO electrodes also exhibit superior selectivity toward the target contaminant (i.e. Hg2+ ion). Accordingly, the functionalized GQDs pave the way for engineering the electrochemical sensors capable of detecting toxic Hg2+ ions with superb sensitivity and selectivity.

Oxidation efficiency of glucose using viologen mediators for glucose fuel cell applications with non-precious anodes

Glucose is a potential source of energy for fuel cell applications. However, its complete oxidation has been a challenge. Dimethyl viologen, as an electron mediator, has been shown to promote high levels of glucose oxidation under aerobic conditions. Nevertheless, the efficiency of viologen-mediated glucose oxidation has been low in electrochemical experiments. In this study, viologen-mediated oxidation of glucose was investigated under anaerobic electrochemical conditions to understand the factors that impact the oxidation efficiency. Of particular interest was the improvement of electrochemical oxidation for glucose fuel cell applications. An experimental cell was developed to electrochemically reoxidize the mediator as it was homogeneously reduced by glucose under anaerobic conditions. In contrast, the mediator was reoxidized by direct reaction with oxygen under aerobic conditions. The aerobic oxidation efficiency was 75%, three times larger than the maximum efficiency in the electrochemical cell. 13C-NMR results show that the main product formed under aerobic conditions was formic acid, whereas glycolic acid was the principal product formed in the electrochemical cell. Carbonate was only formed under aerobic conditions. Therefore, the use of oxygen to reoxidize the mediator also directly influenced the glucose oxidation pathway. In the electrochemical cell, the oxidation efficiency depended on the electrochemical reaction rate of the mediator and was higher at faster rates. The efficiency also depended on the initial molar ratio of the mediator to glucose. The maximum oxidation efficiency of glucose in the electrochemical cell was approximately 22%, which is about three times larger than the maximum efficiency for precious-metal-based anodes.