Low Concentrations Of Nitric Oxide Research Articles

Nitric oxide has diverse effects on head and neck cancer cell proliferation and glycolysis.

Glycolysis is a key energy-providing process and one of the hallmarks of cancer. Nitric oxide (NO), a free radical molecule, regulates glycolysis in various cancers. NO can alter the cell cycle and apoptosis in head and neck squamous cell carcinoma (HNSCC) cells. However, the effect of NO on glycolysis in HNSCC cells remains unresolved. The present study investigated the effects of NO on cell proliferation, glucose transporter (GLUT) gene expression and glycolytic indicators in HNSCC cell lines. Two pairs of isogenic HNSCC cell lines, HN18/HN17 and HN30/HN31, were treated with a NO donor, diethylamine NONOate (DEA-NONOate), for 24, 48 and 72 h. Cell proliferation was assessed using MTT assay and NO concentration was measured using the Griess Reagent System. GLUT1, GLUT2, GLUT3, and GLUT4 gene expression was analyzed using reverse transcription-quantitative PCR. Furthermore, hexokinase (HK) activity and lactate production were measured in NO-treated cells using colorimetric assay. NO exhibited concentration-dependent pro- and anti-proliferative effects on the HNSCC cell lines. Lower NO concentrations (5-200 µM) had pro-proliferative effects, whereas NO >200 µM had an anti-proliferative effect on HNSCC cells. NO (5 µM) promoted proliferation and glycolysis in HN18 cells by upregulating GLUT1 and GLUT2 gene expression and increasing HK activity and lactate levels. At 5-20 µM, NO-induced HN17 and HN30 cells demonstrated enhanced proliferation and GLUT2, GLUT3 and GLUT4 gene expression, whereas the glycolytic pathway was not affected. In conclusion, the present study demonstrated distinct proliferative effects of NO on HNSCC cells. NO may promote cell proliferation by stimulating glucose consumption and the glycolytic rate in HN18 cells. The effects of NO in other cell lines may be mediated by a non-glycolysis mechanism and require further investigation.

Direct recovery of electro-synthesized ammonia from low-concentration nitric oxide using pulse electrodeposited Cu/C catalyst in a catholyte-free system

Electrochemical production of ammonia (NH3) from nitric oxide (NO) offers a sustainable and environmentally friendly way to convert a nitrogenous pollutant into a valuable chemical feedstock and energy carrier. However, practical challenges in the electrochemical NO-to-NH3 conversion stem from mass transport limitations due to low NO concentrations in real-world streams and the need for post-purification of synthesized NH3. In this study, by synergistically developing an electrocatalyst (pulse-electrodeposited copper) and implementing a catholyte-free cell configuration with advantages of (i) facile NO transport, (ii) inhibited side reaction, and (iii) direct NH3 recovery in an external acid, we showcase an NH3 Faradaic efficiency of 85.6 % and a production rate of 53.4 μmol cm−2h−1 starting from 500 ppm NO. Crucially, the electro-synthesized NH3 was directly recovered as a high-purity aqueous ammonium sulfate solution comparable to industrial-grade quality. This approach opens the door to transforming waste into resources in a more energy-efficient and straightforward manner.

Aqueous Electroreduction of Nitric Oxide to Ammonia at Low Concentration via Vacancy Engineered FeOCl

AbstractElectroreduction of nitric oxide (NO) to NH3 (NORR) has gained extensive attention for the sake of low carbon emission and air pollutant treatment. Unfortunately, NORR is greatly hindered by its sluggish kinetics, especially under low concentrations of NO. Herein, we developed a chlorine (Cl) vacancy strategy to overcome this limitation over FeOCl nanosheets (FeOCl‐VCl). Density functional theory (DFT) calculations revealed that the Cl vacancy resulted in defective Fe with sharp d‐states characteristics in FeOCl‐VCl to enhance the absorption and activation of NO. In situ X‐ray absorption near‐edge structure (XANES) and attenuated total reflection‐infrared spectroscopy (ATR‐IR) verified the lower average oxidation state of defective Fe to enhance the electron transfer for NO adsorption/activation and facilitate the generation of key NHO and NHx intermediates. As a result, the FeOCl‐VCl exhibited superior NORR activities with the NH3 Faradaic efficiency up to 91.1 % while maintaining a high NH3 yield rate of 455.4 μg cm−2 h−1 under 1.0 vol % NO concentration, competitive with those of previously reported literatures under higher NO concentration. Further, the assembled Zn‐NO battery utilizing FeOCl‐VCl as cathode delivered a record peak power density of 6.2 mW cm−2, offering a new route for simultaneous NO removal, NH3 production, and energy supply.

Aqueous Electroreduction of Nitric Oxide to Ammonia at Low Concentration via Vacancy Engineered FeOCl.

Electroreduction of nitric oxide (NO) to NH3 (NORR) has gained extensive attention for the sake of low carbon emission and air pollutant treatment. Unfortunately, NORR is greatly hindered by its sluggish kinetics, especially under low concentrations of NO. Herein, we developed a chlorine (Cl) vacancy strategy to overcome this limitation over FeOCl nanosheets (FeOCl-VCl ). Density functional theory (DFT) calculations revealed that the Cl vacancy resulted in defective Fe with sharp d-states characteristics in FeOCl-VCl to enhance the absorption and activation of NO. In situ X-ray absorption near-edge structure (XANES) and attenuated total reflection-infrared spectroscopy (ATR-IR) verified the lower average oxidation state of defective Fe to enhance the electron transfer for NO adsorption/activation and facilitate the generation of key NHO and NHx intermediates. As a result, the FeOCl-VCl exhibited superior NORR activities with the NH3 Faradaic efficiency up to 91.1 % while maintaining a high NH3 yield rate of 455.4 μg cm-2 h-1 under 1.0 vol % NO concentration, competitive with those of previously reported literatures under higher NO concentration. Further, the assembled Zn-NO battery utilizing FeOCl-VCl as cathode delivered a record peak power density of 6.2 mW cm-2 , offering a new route for simultaneous NO removal, NH3 production, and energy supply.

Nitric oxide transport in carotid bifurcation after different stent interventions: a numerical study

Stent restenosis and late thrombosis compromise endovascular stent implantation clinical benefit, and the mechanism is unclear. Since nitric oxide (NO) plays a pivotal role in maintaining vascular homeostasis, we believe that stenting can affect NO concentration in the host artery, thereby contributing to postoperative adverse events. We numerically investigated NO concentration after stenting based on the patient-specific carotid to verify this hypothesis. The simulation revealed that stent implantation caused blood flow disturbance, a low wall shear stress, and a significant decrease in NO on the luminal surface, especially in the region of the stented segment. Moreover, severe damage to the artery wall or low blood flow, leading to a low NO generation rate, would induce relatively low NO level in the stented segment. Additionally, we demonstrated that NO distribution might be affected by the combination of stent struts and carotid bifurcation geometry, while the host arterial configuration might play a leading role in the distribution of NO concentration. In conclusion, the carotid artery had a relatively low NO concentration level near stent struts, especially at the severely injured artery, low blood flow, long stenting, and complex host artery which might lead to a genesis/development of adverse events after that intervention.

Cu@Co with Dilatation Strain for High-Performance Electrocatalytic Reduction of Low-Concentration Nitric Oxide.

Electrocatalytic reduction of nitric oxide (NO) to ammonia (NH3 ) is a clean and sustainable strategy to simultaneously remove NO and synthesize NH3 . However, the conversion of low concentration NO to NH3 is still a huge challenge. In this work, the dilatation strain between Cu and Co interface over Cu@Co catalyst is built up and investigated for electroreduction of low concentration NO (volume ratio of 1%) to NH3 . The catalyst shows a high NH3 yield of 627.20µg h-1 cm-2 and a Faradaic efficiency of 76.54%. Through the combination of spherical aberration-corrected transmission electron microscopy and geometric phase analyses, it shows that Co atoms occupy Cu lattice sites to form dilatation strain in the xy direction within Co region. Further density functional theory calculations and NO temperature-programmed desorption (NO-TPD) results show that the surface dilatation strain on Cu@Co is helpful to enhance the NO adsorption and reduce energy barrier of the rate-determining step (*NO to *NOH), thereby accelerating the catalytic reaction. To simultaneously realize NO exhaust gas removal, NH3 green synthesis, and electricity output, a Zn-NO battery with Cu@Co cathode is assembled with a power density of 3.08mW cm-2 and an NH3 yield of 273.37µg h-1 cm-2 .

Experimental Investigation of the Effect of Superheated Liquid Fuel Injection on the Combustion Characteristics of Lean Premixed Flames

Abstract The effect of superheated liquid fuel injection on the performance and emissions of a single nozzle combustor was investigated. Combustion of the lean premixed flames was achieved using a combination of jet and swirl as a stabilization method. In a nonreactive setup, the optimum transition temperature of Jet A-1 fuel from liquid to superheated vaporized state was analyzed. In a subsequent reactive setup, a series of tests were conducted with the liquid fuel at low and elevated temperatures. The experiments were conducted at ambient pressure and various air and fuel preheat temperatures, axial swirlers, thermal powers, adiabatic flame temperatures, and flame tube diameters. Concentrations of nitric oxide (NOx) and carbon monoxide (CO) in the flue gas were measured. The operating conditions were systematically selected according to the design of experiments (DOE) method. The results showed that the adiabatic flame temperature caused the most significant change in combustion emissions and the position and shape of the reaction zone, while the superheated fuel injection had only a minor effect because the liquid fuel droplets were largely vaporized before entering the reaction zone through the integration of a swirler and a prefilmer. The use of the axial swirler and prefilmer allowed the combustor to operate in both spray and fully vaporized fuel conditions. As a result, very low emission concentrations of NOx (≈5 ppm) and CO (≈6 ppm) were achieved. The median flame length and height above the burner of the characterized flames showed competitive values of 32 mm and 50 mm, respectively. Lean blowout limits of less than 1500 K were achieved. Two different flame modes were observed during the experiments. By increasing the bulk velocity of the combustor, its hysteresis was resolved, resulting in stable and reliable flames with a wide low-NOx operating range.

Association between endothelial nitric oxide synthase (eNOS) gene variants and nitric oxide production in preeclampsia: a case–control study in Ghana

Evidence suggests that a major cause of PE is endothelial dysfunction emanating from the reduced bioavailability of Nitric oxide (NO). Variants of endothelial nitric oxide synthase (eNOS) gene may lead to decreased NO levels. We explored the association between eNOS gene variants and nitric oxide levels among preeclamptic women in the Ghanaian population. This case–control study included 75 preeclamptic women and 75 healthy normotensive pregnant women attending antenatal care at the Nkawie-Toase Government Hospital, Ghana. A well-structured questionnaire was used to collect socio-demographic, obstetric and clinical data. Blood was obtained for DNA extraction; the gene variants were determined using PCR and RFLP. Preeclamptic women had significantly lower NO concentration compared to the normotensives (p < 0.0001) and was significantly different between VNTR variants (p < 0.0001). A significant difference in VNTR intron 4 distribution was also observed between the preeclamptic and normotensive women with 4c4c” (12.0%) and “4a4c” (1.3%) genotypes found predominantly in preeclamptic women (p < 0.0001). There was significantly higher distribution of “TC” genotype in preeclamptic women (44.0%) compared to normotensives (22.7%) (p = 0.019). However, possessing “4a4b” (cOR: 0.17, 95% CI 0.04–0.64) and “4b4b” (cOR: 0.09, 95% CI 0.02–0.38) significantly decreased the likelihood of experiencing preeclampsia by 83% and 91% respectively. Nitric oxide is reduced in preeclamptic women. NO levels in preeclampsia are altered by VNTR intron 4 variants but not T786C variants. Possessing VNTR intron 4 “4b” allele decreases the risk of PE while the “4c” allele increases the risk of PE. There is the need for eNOS variant screening and nitric oxide estimation among pregnant women for early prediction of women at risk of preeclampsia.

Electrochemically-mediated reactive separation of nitric oxide into nitrate using iron chelate

Valorization of nitric oxide is a promising solution for addressing the environmental and resource issues related to the nitrogen cycle. However, low concentrations of nitric oxide combined with impurities in exhaust streams limit its potential, and it requires extensive energy to produce high-purity nitric oxide. Here, we propose a synergistic reactive separation system that combines iron-chelate selective absorption with an electrochemical reaction to convert nitric oxide to nitrate. Among the iron-based chelates tested, EDTA was found to be the most effective in capturing gas-phase nitric oxide. Direct electrochemical oxidation of Fe-EDTA-NO solution exhibited Faradaic efficiency and a partial current density toward nitrate of 70% and 30.1 mA cm−2 at 2.2 V vs RHE and pH 7, resulting in a 43-fold enhancement of nitrate partial current density and a 2-fold improvement in Faradaic efficiency compared to simple purging without selective absorbent. Nitrate was then selectively recovered from the Fe-EDTA system using simple polarity reversal following electrooxidation with a separation factor of 13 over background sulfate. This study offers a new approach to gas-phase NO remediation and valorization using an electrified means.

Nitric oxide: an old drug but with new horizons in ophthalmology-a narrative review.

Based on basic knowledge and prior research on nitric oxide (NO), the potential of NO for treating eye diseases is reviewed, and the possibility of NO-based eye drops in clinical practice and the future potential of NO in ophthalmology are discussed. A PubMed search was performed for English-language original reports and reviews using the following key words: nitric oxide, eye, ocular, and drug. NO is synthesized in the human body by NO synthase (NOS) from L-arginine or through enzyme-dependent reduction of dietary nitrate. Three types of NOS (eNOS, nNOS, and iNOS) are abundantly expressed in the eye under normal physiologic or pathologic conditions. The biological effect of NO in the eye is dose dependent. Low intraocular NO concentrations, produced by eNOS or nNOS, have various cellular effects, including vasodilation, intraocular pressure (IOP) regulation, and neuroprotection. iNOS induced under pathologic ocular conditions produces high NO concentrations in the local environment and mediates tissue inflammation, ocular cell apoptosis, and neurodegeneration. In particular, increased iNOS has been reported in glaucoma and retinal ischemic or degenerative diseases. NO plays a vital role in ocular injury. NO can facilitate ocular surface wound healing while eradicating pathogens such as bacteria and Acanthamoeba in chemical burns or infectious keratitis. Furthermore, NO has antifibrotic activity via the cyclic guanosine monophosphate (cGMP) signaling pathway. NO causes smooth muscle relaxation, which can be used to inhibit myopia progression in children. NO can be a stem cell modulator and may help in treating ocular stem cell disorders. Because of its diverse biologic effects, NO can be a key player in regulating ocular inflammation in various ocular diseases, aiding ocular surface wound healing, controlling IOP in glaucoma, alleviating retinal disease, and suppressing myopia progression. Although there remain limitations to the effective use of highly unstable state, gaseous NO, the role of NO in the field of ophthalmology can be greatly expanded through the development of novel NO donors and effective delivery platforms.

An efficient Co-Ni hydrous oxide catalyst for elimination of NO pollutant in semi-enclosed spaces at ambient temperature

Co-Ni bimetallic hydrous oxides are applied for the abatement of low-concentration nitric oxide (NO) pollution in semi-enclosed spaces. The textural properties of these materials are characterized by surface area/porosity analyzer, SEM/TEM imaging coupled with elemental mapping. In situ DRIFTS, XPS and temperature-programmed desorption are applied to elucidate the NO trapping mechanisms. The NO storage capacity is tested by flowing low-concentration NO in O2/He through these materials at ambient temperature. The Co/Ni molar ratio is found to greatly influence the surface area, pore structure and morphology of the Co-Ni bimetallic hydrous oxides, thus affecting the elimination performance of low-concentration NO. During NO storage, nitrite formation is found to be associated with Co, and nitrate formation is found to be associated with Ni. In the Co-Ni bimetallic materials, a synergy exists where nitrite formed on Co is further oxidized to nitrate by lattice oxygen on Ni. Finally, these materials are readily regenerated by washing with Na2S2O8 aqueous solution.

Photocatalytic NO removal based on TiO2 photonic crystals through slow photon effect

Photocatalysis based on TiO2 nanomaterials demonstrates great potential in low-concentration nitric oxide (NO) removal. The utilization of solar energy is critical for increasing the NO removal rate. Here, TiO2 photonic crystal (TiO2-PC) is synthesized for efficiently photocatalytic NO removal by improving the utilization of sunlight in the visible region. Under solar irradiation, the transient photocurrent response and NO removal ratio of TiO2-PC is ∼2.3 times and about double that of pristine TiO2-film. The slow photon effect, as verified by reflection and absorption spectra. This work provides a promising approach to fabricating TiO2-based photocatalysts for highly efficient NO removal.

Removal of NO at low concentrations from polluted air in semi-closed environments by activated biochars from renewables feedstocks

Efficient measures are urgently required in large cities for nitric oxide (NO) elimination from air in urban semi-closed environments (parking lots and tunnels), characterized by low NO concentrations (<10 ppmv) and temperatures. One of the most promising abatement alternatives is the NO oxidation to NO2, which can be further easily captured in an alkali solution or over a porous solid. However, most of the research devoted to this topic is focused on the elimination of NO from fuel exhaust gases, with high NO concentrations (400–2000 ppmv). In this work, sustainable and low-cost activated biochars of different origin and having very different ash contents were employed in NO removal at very low concentrations. Thus, low ash content forestry (oak woodchips, OAK) and high ash content from agriculture (oilseed rape straw, OSR) biochars were subjected to physical activation with CO2 at 900 °C (OAK550-A900CO2 and OSR700-A900CO2, respectively). The NO removal performance tests of such activated carbons were carried out at different experimental conditions: i.e., temperature, relative humidity (0–50 vol% RH), NO-containing gas (N2 or air), amount of activated carbon, and NO concentration, to assess how the activated biochar properties influence their NO removal capacity. The sample OSR700-A900CO2 contained a higher population of oxygen surface functionalities, which might play an important role in the NO removal efficiency in dry conditions since they could assist NO oxidation on carbon active sites when used above room temperature (50–75 °C). However, at room temperature (25 °C), the presence of narrow micropore size distribution at 6 Å became a more relevant property, since it facilitates an intimate contact between NO and O2. Accordingly, the activated biochar from OAK was much more efficient, achieving complete removal of NO from air flow (dry or with 50 vol% RH) at 25 °C during 400 min of testing, making it an ideal candidate as biofilter for purifying air streams of semi-closed spaces contaminated with low concentrations of NO.

Cobalt and Iron Phthalocyanine Derivatives: Effect of Substituents on the Structure of Thin Films and Their Sensor Response to Nitric Oxide.

In this work, we study the effect of substituents in cobalt(II) and iron(II) phthalocyanines (CoPcR4 and FePcR4 with R = H, F, Cl, tBu) on the structural features of their films, and their chemi-resistive sensor response to a low concentration of nitric oxide. For the correct interpretation of diffractograms of phthalocyanine films, structures of CoPcCl4 and FePcCl4 single crystals were determined for the first time. Films were tested as active layers for the determination of low concentrations of NO (10-1000 ppb). It was found that the best sensor response to NO was observed for the films of chlorinated derivatives MPcCl4 (M = Co, Fe), while the lowest response was in the case of MPc(tBu)4 films. FePcCl4 films exhibited the maximal response to NO, with a calculated limit of detection (LOD) of 3 ppb; the response and recovery times determined at 30 ppb of NO were 30 s and 80 s, respectively. The LOD of a CoPcCl4 film was 7 ppb. However, iron phthalocyanine films had low stability and their sensitivity to NO decreased rapidly over time, while the response of cobalt phthalocyanine films remained stable for at least several months. In order to explain the obtained regularities, quantum chemical calculations of the binding parameters between NO and phthalocyanine molecules were carried out. It was shown that the binding of NO to the side atoms of phthalocyanines occurred through van der Waals forces, and the values of the binding energies were in direct correlation with the values of the sensor response to NO.

Defective TiO2- x for High-Performance Electrocatalytic NO Reduction toward Ambient NH3 Production.

Synthesis of green ammonia (NH3 ) via electrolysis of nitric oxide (NO) is extraordinarily sustainable, but multielectron/proton-involved hydrogenation steps as well as low concentrations of NO can lead to poor activities and selectivities of electrocatalysts. Herein, it is reported that oxygen-defective TiO2 nanoarray supported on Ti plate (TiO2- x /TP) behaves as an efficient catalyst for NO reduction to NH3 . In 0.2m phosphate-buffered electrolyte, such TiO2- x /TP shows competitive electrocatalytic NH3 synthesis activity with a maximum NH3 yield of 1233.2µgh-1 cm-2 and Faradaic efficiency of 92.5%. Density functional theory calculations further thermodynamically faster NO deoxygenation and protonation processes on TiO2- x (101) compared to perfect TiO2 (101). And the low energy barrier of 0.7eV on TiO2- x (101) for the potential-determining step further highlights the greatly improved intrinsic activity. In addition, a Zn-NO battery is fabricated with TiO2- x /TP and Zn plate to obtain an NH3 yield of 241.7µgh-1 cm-2 while providing a peak power density of 0.84mWcm-2 .

H-NOX Regulates Biofilm Formation in Agrobacterium Vitis in Response to NO.

Transitions between motile and biofilm lifestyles are highly regulated and fundamental to microbial pathogenesis. H-NOX (heme-nitric oxide/oxygen-binding domain) is a key regulator of bacterial communal behaviors, such as biofilm formation. A predicted bifunctional cyclic di-GMP metabolizing enzyme, composed of diguanylate cyclase and phosphodiesterase (PDE) domains (avi_3097), is annotated downstream of an hnoX gene in Agrobacterium vitis S4. Here, we demonstrate that avH-NOX is a nitric oxide (NO)-binding hemoprotein that binds to and regulates the activity of avi_3097 (avHaCE; H-NOX-associated cyclic di-GMP processing enzyme). Kinetic analysis of avHaCE indicates a ∼four-fold increase in PDE activity in the presence of NO-bound avH-NOX. Biofilm analysis with crystal violet staining reveals that low concentrations of NO reduce biofilm growth in the wild-type A. vitis S4 strain, but the mutant ΔhnoX strain has no NO phenotype, suggesting that H-NOX is responsible for the NO biofilm phenotype in A. vitis. Together, these data indicate that avH-NOX enhances cyclic di-GMP degradation to reduce biofilm formation in response to NO in A. vitis.

Fabrication of ultra-sensitive NO sensor based on vacuum selenized WSe2nanorods

Nitric oxide (NO) is one of the hazardous gases in air pollution, which is associated with surface ozone pollution and acid rain and affects vital human organs. Even a lower NO concentration is crucial to diagnose and track for environmental monitoring, air quality assurance, industries, and automotive machinery. Therefore, the fabrication of very sensitive and portable NO detectors that can detect the gas at relatively low concentrations (ppb level) is crucial for diagnosing and tracking the gas. To address these challenges, we have developed a WSe2 nanorods-based ultra-sensitive gas sensor that can detect small concentrations of NO (100 ppb) in a short period. WSe2 nanorods were grown by DC magnetron sputtering followed by vacuum selenization. The performance of the fabricated gas sensor was accessed over a broad range (100 ppb–20 ppm) of NO concentration at an optimized temperature of 250 °C. The fabricated sensor displays a relative sensor response of 38.98% at 100 ppb, which increases to 88.89% at 20 ppm. The analysis revealed that the grown WSe2 nanorods are sensitive enough to detect NO at very low concertation with a calculated detection limit of 24 ppb. The NO sensor exhibits high selectivity and stability with fast response/recovery time. The large surface area of grown WSe2 nanorods led to a better charge transfer process, resulting in excellent NO detection. The device revealed potential in environmental monitoring and biomedical applications along with prospects in wearable devices for real-time NO tracking.

Asymmetric dimethylarginine accumulation under hyperglycemia facilitates β-cell apoptosis via inhibiting nitric oxide production

Low concentrations of nitric oxide (NO) produced by constitutive NO synthase (cNOS) has been shown to suppress apoptosis in pancreatic β-cells. In the present study, the influence of asymmetric dimethylarginine (ADMA), the major endogenous inhibitor of NOS, on the apoptosis-suppressive effect of NO was investigated. The expression of dimethylarginine dimethylaminohydrolase 2 (DDAH2), an ADMA-metabolizing enzyme, in INS-1 β-cells and in mouse pancreatic islets was drastically reduced by in vitro exposure to high-concentration glucose (20 mM) and by in vivo treatment of mice with the insulin receptor blocker S661, which resulted in hyperglycemia, respectively. In line with this, a higher ADMA level was observed in INS-1 cells exposed to 20 mM glucose. The treatment of INS-1 cells with ADMA, similarly to with the NOS inhibitor NG-nitro-L-arginine methyl ester, significantly facilitated 20 mM glucose-induced increase in cleaved caspase-3 protein expression. Furthermore, increased protein expression of cleaved caspase-3 and CHOP was observed in INS-1 cells with knockdown of DDAH2. These results suggest that ADMA accumulation through a decrease in DDAH2 expression in β-cells, which is induced under hyperglycemic conditions, facilitates β-cell apoptosis through suppression of cNOS-mediated NO production.

Ultrahigh sensitive NO sensor based on WO3 film with ppb-level sensitivity

Nitric oxide (NO) is one of the hazardous gases which directly affect the vital organs of human beings. An accurate identification is essential for air quality assurance, environmental monitoring, automotive technology, and other industrial processes. Herein, we report nanostructured tungsten oxide (WO3) thin-film grown on SiO2 substrate under controlled oxidation conditions for NO sensing. The nanostructured-WO3 film's monoclinic phase has an average crystallite size of 12.89 nm, a lattice strain of 20.56, and an optical band gap of 2.89 eV. The fabricated device demonstrates high selectivity, stability, and faster response/recovery time with a sensor response of 1.26 for 100 ppb NO concentration, which increases to an ultra-high response (>25) for 1 ppm at 250 °C with a detection limit of ∼4 ppb. Ultrahigh response of the sensors is due to high specific surface area and effective gas diffusion ability, which lead to potential applications in low concentration NO detection.

Spectroscopic Characterization of a Diferric Mycobacterial Hemerythrin-Like Protein with Unprecedented Reactivity toward Nitric Oxide.

Hemerythrin-like proteins (HLPs) are broadly distributed across taxonomic groups and appear to play highly diverse functional roles in prokaryotes. Mycobacterial HLPs contribute to the survival of these pathogenic bacteria in mammalian macrophages, but their modes of action remain unclear. A recent crystallographic characterization of Mycobacterium kansasii HLP (Mka-HLP) revealed the unexpected presence of a tyrosine sidechain (Tyr54) near the coordination sphere of one of the two iron centers. Here, we show that Tyr54 is a true ligand to the Fe2(III) ion which, in conjunction with the presence of a μ-oxo group bridging the two iron(III), brings unique reactivity toward nitric oxide (NO). Monitoring the titration of Mka-HLP with NO by Fourier-transform infrared and electron paramagnetic resonance spectroscopies shows that both diferric and diferrous forms of Mka-HLP accumulate an uncoupled high-spin and low-spin {FeNO}7 pair. We assign the reactivity of the diferric protein to an initial radical reaction between NO and the μ-oxo bridge to form nitrite and a mixed-valent diiron center that can react further with NO. Amperometric measurements of NO consumption by Mka-HLP confirm that this reactivity can proceed at low micromolar concentrations of NO, before additional NO consumption, supporting a NO scavenging role for mycobacterial HLPs.