μM NO2 Research Articles

Improvement of On-Site Sensor for Simultaneous Determination of Phosphate, Silicic Acid, Nitrate plus Nitrite in Seawater.

Accurate, on-site determinations of macronutrients (phosphate (PO43−), nitrate (NO3−), and silicic acid (H4SiO4)) in seawater in real time are essential to obtain information on their distribution, flux, and role in marine biogeochemical cycles. The development of robust sensors for long-term on-site analysis of macronutrients in seawater is a great challenge. Here, we present improvements of a commercial automated sensor for nutrients (including PO43−, H4SiO4, and NO2− plus NO3−), suitable for a variety of aquatic environments. The sensor uses the phosphomolybdate blue method for PO43−, the silicomolybdate blue method for H4SiO4 and the Griess reagent method for NO2−, modified with vanadium chloride as reducing agent for the determination of NO3−. Here, we report the optimization of analytical conditions, including reaction time for PO43− analysis, complexation time for H4SiO4 analysis, and analyte to reagent ratio for NO3− analysis. The instrument showed wide linear ranges, from 0.2 to 100 μM PO43−, between 0.2 and 100 μM H4SiO4, from 0.5 to 100 μM NO3−, and between 0.4 and 100 μM NO2−, with detection limits of 0.18 μM, 0.15 μM, 0.45 μM, and 0.35 μM for PO43−, H4SiO4, NO3−, and NO2−, respectively. The analyzer showed good precision with a relative standard deviation of 8.9% for PO43−, 4.8% for H4SiO4, and 7.4% for NO2− plus NO3− during routine analysis of certified reference materials (KANSO, Japan). The analyzer performed well in the field during a 46-day deployment on a pontoon in the Kiel Fjord (located in the southwestern Baltic Sea), with a water supply from a depth of 1 m. The system successfully collected 443, 440, and 409 on-site data points for PO43−, Σ(NO3− + NO2−), and H4SiO4, respectively. Time series data agreed well with data obtained from the analysis of discretely collected samples using standard reference laboratory procedures and showed clear correlations with key hydrographic parameters throughout the deployment period.

Maintenance power requirements of anammox bacteria "Candidatus Brocadia sinica" and "Candidatus Scalindua sp."

Little is known about the cell physiology of anammox bacteria growing at extremely low growth rates. Here, "Candidatus Brocadia sinica" and "Candidatus Scalindua sp." were grown in continuous anaerobic membrane bioreactors (MBRs) with complete biomass retention to determine maintenance energy (i.e., power) requirements at near-zero growth rates. After prolonged retentostat cultivations, the specific growth rates (μ) of "Ca. B. sinica" and "Ca. Scalindua sp." decreased to 0.000023 h-1 (doubling time of 1255 days) and 0.000157 h-1 (184 days), respectively. Under these near-zero growth conditions, substrate was continuously utilized to meet maintenance energy demands (me) of 6.7 ± 0.7 and 4.3 ± 0.7 kJ mole of biomass-C-1 h-1 for "Ca. B. sinica" and "Ca. Scalindua sp.", which accorded with the theoretically predicted values of all anaerobic microorganisms (9.7 and 4.4 kJ mole of biomass-C-1 h-1at 37 °C and 28 °C, respectively). These me values correspond to 13.4 × 10-15 and 8.6 × 10-15 watts cell-1 for "Ca. B. sinica" and "Ca. Scalindua sp.", which were five orders of magnitude higher than the basal power limit for natural settings (1.9 × 10-19 watts cells-1). Furthermore, the minimum substrate concentrations required for growth (Smin) were calculated to be 3.69 ± 0.21 and 0.09 ± 0.05 μM NO2- for "Ca. B. sinica" and "Ca. Scalindua sp.", respectively. These results match the evidence that "Ca. Scalindua sp." with lower maintenance power requirement and Smin are better adapted to energy-limited natural environments than "Ca. B. sinica", suggesting the importance of these parameters on ecological niche differentiation in natural environments.

Systemic Inflammation (C-Reactive Protein) in Older Chinese Adults Is Associated with Long-Term Exposure to Ambient Air Pollution.

There is an established association between air pollution and cardiovascular disease (CVD), which is likely to be mediated by systemic inflammation. The present study evaluated links between long-term exposure to ambient air pollution and high-sensitivity C reactive protein (hs-CRP) in an older Chinese adult cohort (n = 7915) enrolled in the World Health Organization (WHO) study on global aging and adult health (SAGE) China Wave 1 in 2008–2010. Multilevel linear and logistic regression models were used to assess the associations of particulate matter (PM) and nitrogen dioxide (NO2) on log-transformed hs-CRP levels and odds ratios of CVD risk derived from CRP levels adjusted for confounders. A satellite-based spatial statistical model was applied to estimate the average community exposure to outdoor air pollutants (PM with an aerodynamic diameter of 10 μm or less (PM10), 2.5 μm or less (PM2.5), and 1 μm or less (PM1) and NO2) for each participant of the study. hs-CRP levels were drawn from dried blood spots of each participant. Each 10 μg/m3 increment in PM10, PM2.5, PM1, and NO2 was associated with 12.8% (95% confidence interval; (CI): 9.1, 16.6), 15.7% (95% CI: 10.9, 20.8), 10.2% (95% CI: 7.3, 13.2), and 11.8% (95% CI: 7.9, 15.8) higher serum levels of hs-CRP, respectively. Our findings suggest that air pollution may be an important factor in increasing systemic inflammation in older Chinese adults.

Spatio-temporal variations in sulfur-oxidizing and sulfate-reducing bacterial activities during upwelling, off south-west coast of India

Summary The Arabian Sea, off SW India, is becoming more anoxic in recent years. Poor ventilation affects microbial degradation of organic matter in the oxygen minimum zone (≤2.85 ml l−1 O2, ≤0.02 μM NO2) and the anoxic marine zone (≤0.09 ml l−1 O2, ≥0.5 μM NO2). We posit that one of the reasons at the microbial level could be due to a more prominent increase in sulfate-reducing activity (SRA), than sulfur-oxidizing activity (SOA). Hence, the objective was to measure the extent to which SOA can counter the effect of SRA. We, therefore examined these activities along with relevant environmental variables from 2009 to 2011 off Kochi (9.55°N–75.33°E) and Trivandrum (8.26°N–76.50°E), covering the three phases of upwelling. SRA was measured radiometrically using 35S, and SOA by iodometry. Off Kochi, the SOA of the water column increased 6× (194–1151 μM d−1) and SRA 4× (13–54 nM d−1) from phase I to III. Off Trivandrum, the increase in SOA was 1.7× (339–560 μM d−1) and SRA 7× (24–165 nM d−1) contributing to the build-up of reducing/oxidizing conditions. This increase in SOA moderates the effect of increase in SRA. Besides, the average concentrations of dissolved oxygen and nitrite off Trivandrum were 1.80 ± 1.66, 1.48 ± 1.55, 1.93 ± 1.86 ml l−1 and 0.14 ± 0.14, 1.69 ± 0.67, 0.34 ± 0.42 μM during the three phases respectively. Hence, it is suggested that the coastal waters examined in this study could probably be between oxygen minimum zone (OMZ) and anoxic minimum zone (AMZ) in patches temporarily. The present paper highlights the interactions between sulfate-reducing and sulfur-oxidizing activities, during upwelling for the first time in these waters. These observations give an important and timely insight into the implications.

Oxidation kinetics and inverse isotope effect of marine nitrite-oxidizing isolates

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 80:289-300 (2017) - DOI: https://doi.org/10.3354/ame01859 Oxidation kinetics and inverse isotope effect of marine nitrite-oxidizing isolates Juliane Jacob1,2,*, Boris Nowka3, Véronique Merten4, Tina Sanders1, Eva Spieck3, Kirstin Dähnke1 1Helmholtz Center Geesthacht, Institute of Coastal Research, Max-Planck-Str. 1, 21502 Geesthacht, Germany 2Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, Bundesstr. 55, 20146 Hamburg, Germany 3Biozentrum Klein Flottbek, Department of Microbiology and Biotechnology, University of Hamburg, Ohnhorststr. 18, 22609 Hamburg, Germany 4GEOMAR Helmholtz Center for Ocean Research Kiel, Wischhofstr. 1-3, 24148 Kiel, Germany *Corresponding author: juliane.jacob@uni-hamburg.de ABSTRACT: Nitrification, the step-wise oxidation of ammonium to nitrite and nitrate, is important in the marine environment because it produces nitrate, the most abundant marine dissolved inorganic nitrogen (DIN) component and N-source for phytoplankton and microbes. This study focused on the second step of nitrification, which is carried out by a distinct group of organisms, nitrite-oxidizing bacteria (NOB). The growth of NOB is characterized by nitrite oxidation kinetics, which we investigated for 4 pure cultures of marine NOB (Nitrospina watsonii 347, Nitrospira sp. Ecomares 2.1, Nitrococcus mobilis 231, and Nitrobacter sp. 311). We further compared the kinetics to those of non-marine species because substrate concentrations in marine environments are comparatively low, which likely influences kinetics and highlights the importance of this study. We also determined the isotope effect during nitrite oxidation of a pure culture of Nitrospina (Nitrospina watsonii 347) belonging to one of the most abundant marine NOB genera, and for a Nitrospira strain (Nitrospira sp. Ecomares 2.1). The enzyme kinetics of nitrite oxidation, described by Michaelis-Menten kinetics, of 4 marine genera are rather narrow and fall in the low end of half-saturation constant (Km) values reported so far, which span over 3 orders of magnitude between 9 and >1000 µM NO2-. Nitrospina has the lowest Km (19 µM NO2-), followed by Nitrobacter (28 µM NO2-), Nitrospira (54 µM NO2-), and Nitrococcus (120 µM NO2-). The isotope effects during nitrite oxidation by Nitrospina watsonii 347 and Nitrospira sp. Ecomares 2.1 were 9.7 ± 0.8 and 10.2 ± 0.9‰, respectively. This confirms the inverse isotope effect of NOB described in other studies; however, it is at the lower end of reported isotope effects. We speculate that differences in isotope effects reflect distinct nitrite oxidoreductase (NXR) enzyme orientations. KEY WORDS: Nitrification · Nitrite-oxidizing bacteria · Isotope effect · Enzyme kinetics · Marine environment Full text in pdf format PreviousCite this article as: Jacob J, Nowka B, Merten V, Sanders T, Spieck E, Dähnke K (2017) Oxidation kinetics and inverse isotope effect of marine nitrite-oxidizing isolates. Aquat Microb Ecol 80:289-300. https://doi.org/10.3354/ame01859 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 80, No. 3. Online publication date: December 13, 2017 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2017 Inter-Research.

Association between air pollution and emergency consultations for respiratory diseases

Background: Air pollution has a direct influence on health. Aim: To determine the association between particulate matter and contaminant gas concentrations in the environment with the number of consultations for respiratory diseases in emergency rooms in Metropolitan Santiago, Chile. Material and Methods: During five years, the daily number emergency consultations for respiratory diseases and the daily concentrations of particulate matter and contaminant gases in a community of Santiago, were recorded. The degree of change of these variables during summer and winter was determined. Their correlation coefficients with a 0 to 100 days gap, were calculated. Results: During winter, there was a higher number of consultations and higher pollution levels, except for O3 , which increased in summer. There were positive correlations between the concentrations of different pollutants (mainly 2.5 and 10 μm particulate matter, CO and NO2 ). There was a negative association between consultations for respiratory diseases and O3 concentrations, an almost negligible association with SO2 and variable positive and significant associations with the concentration of other pollutants, with variations according to the time gap. Conclusions: Pollution and respiratory diseases increase during winter. There are variable associations between pollutant concentrations and the number of consultations for respiratory diseases

A zona incognita surrounds the secondary nitrite maximum in open-ocean oxygen minimum zones

An analytic gap exists between the lower limit of detection of oxygen (O2) by conventional sensors (LOD, ~1 – 3µM O2) and the appearance of NO2– from NO3– reduction (~0.05µM O2), which signifies the secondary nitrite maximum. The near-anoxic milieu where precise O2 measurements could not be made until very recently even by current optodes, favors biogeochemically important redox reactions. The ongoing improvement of optodes might make the gap vanish. Significant O2 levels near the conventional LOD for O2, when accompanied by ~ ≥0.05µM NO2–, must be erroneous and should be deleted from historical data going back to the 1930s.

Enrichment and Physiological Characterization of a Cold-Adapted Nitrite-Oxidizing Nitrotoga sp. from an Eelgrass Sediment.

Nitrite-oxidizing bacteria (NOB) are responsible for the second step of nitrification in natural and engineered ecosystems. The recently discovered genus Nitrotoga belongs to the Betaproteobacteria and potentially has high environmental importance. Although environmental clones affiliated with Nitrotoga are widely distributed, the limited number of cultivated Nitrotoga spp. results in a poor understanding of their ecophysiological features. In this study, we successfully enriched the nonmarine cold-adapted Nitrotoga sp. strain AM1 from coastal sand in an eelgrass zone and investigated its physiological characteristics. Multistep-enrichment approaches led to an increase in the abundance of AM1 to approximately 80% of the total bacterial population. AM1 was the only detectable NOB in the bacterial community. The 16S rRNA gene sequence of AM1 was 99.6% identical to that of "Candidatus Nitrotoga arctica," which was enriched from permafrost-affected soil. The highest nitrogen oxidation rate of AM1 was observed at 16°C. The half-saturation constant (Km ) and the generation time were determined to be 25 μM NO2- and 54 h, respectively. The nitrite oxidation rate of AM1 was stimulated at concentrations of <30 mM NH4Cl but completely inhibited at 50 mM NH4Cl. AM1 can grow well under specific environmental conditions, such as low temperature and in the presence of a relatively high concentration of free ammonia. These results help improve our comprehension of the functional importance of NitrotogaIMPORTANCE Nitrite-oxidizing bacteria (NOB) are key players in the second step of nitrification, which is an important process of the nitrogen cycle. Recent studies have suggested that the organisms of the novel NOB genus Nitrotoga were widely distributed and played a functional role in natural and engineered ecosystems. However, only a few Nitrotoga enrichments have been obtained, and little is known about their ecology and physiology. In this study, we successfully enriched a Nitrotoga sp. from sand in a shallow coastal marine ecosystem and undertook a physiological characterization. The laboratory experiments showed that the Nitrotoga enrichment culture could adapt not only to low temperature but also to relatively high concentrations of free ammonia. The determination of as-yet-unknown unique characteristics of Nitrotoga contributes to the improvement of our insights into the microbiology of nitrification.

In situ assay of nitrate reductase activity using portable water bath.

In environmental research (i.e., plant ecophysiology, environmental microbiology, and environmental chemistry), some assays require incubation of samples at controlled temperature and darkness. Until now, due to a lack of equipment providing such possibility in situ, researchers had to move collected samples to the laboratory for incubation. Obviously, a delayed incubation and the ex situ conditions could seriously affect the assays' results. A good example of analysis where water bath use is needed is the nitrate reductase activity (NRA) in vivo assay where plant tissue samples are incubated in buffer solution at a predetermined temperature. We designed a transportable water bath with a temperature control which enables in situ measurements in many types of environmental studies. The presented device is small in size featuring a thermally insulated chamber and an electronically controlled thermostat system powered by a 12-V battery. Due to its modular design, it can be transported comfortably in difficult terrain. The incubation process can be carried out continuously in stable temperature and darkness. In order to examine the field usability of the presented device, we conducted measurements of plant nitrate reductase activity in difficult field conditions. The in situ assays were carried out at high altitudes in the Karkonosze mountains, SW Poland. The NRA was studied in two alpine species (Deschampsia caespitosa and Homogyne alpina). Our results showed low NR activity in H. alpina (mean 0.31μM NO2 g-1 DW h-1) and higher NRA in D. caespitosa (mean 2.7μM NO2 g-1 DW h-1). The obtained results were highly reproducible and had small variability (low standard error values).

Increased NO Sensitivity is Associated with Maintained Coronary Microvascular cGMP‐PDE5 Signaling in Exercising Swine with Multiple Co‐Morbidities

BackgroundMultiple comorbidities, including diabetes mellitus (DM), hypercholesterolemia (HC) and chronic kidney disease (CKD) are thought to cause coronary microvascular dysfunction through a reduction in microvascular NO signaling, leading to impaired myocardial perfusion. Here we investigated whether NO‐cGMP‐PDE5 coronary microvascular signaling is modified in swine with DM+HC+CKD, by studying the vasodilator responses to PDE5 inhibition and to exogenous NO in chronically instrumented swine.Methods and resultsFive female swine (DM+HC+CKD) with Diabetes Mellitus (streptozotocin 3×50mg/kg), chronic kidney disease (renal embolization) were fed high fat diet for 6 months, while six healthy female swine served as controls (CON). Hyperglycemia (21±1.4 vs 8.9±1.5mmol/l in in DM+HC+CKD vs CON, P=0.0002), hypercholesterolemia (7.8±1.0 vs 2.8±1.2mmol/l, P=0.013) and chronic kidney disease (GFR: 123±12 vs 191±9ml/min, P=0.001) were present. Myocardial oxygen delivery was impaired in DM+HC+CKD swine, forcing the myocardium to increase its oxygen extraction both at rest and during exercise (Figure), and resulting in reduced coronary venous oxygen content compared to CON (both P&lt;0.05). PDE5 inhibition with sildenafil (8mg i.v.) decreased myocardial oxygen extraction in both DM+HC+CKD (P=0.016) and CON (P=0.005, Figure), to a similar extent (P=0.34), indicating maintained NO‐cGMP vasodilator influence. As myocardial NO production was decreased (0.19±0.03 vs 0.34±0.13μM NO2−+NO3−/mg protein, P=0.02), we investigated whether an increase in NO sensitivity contributed to maintain NO‐cGMP vasodilator influence, by infusion of the NO donor sodium nitroprusside (SNP). Coronary vascular conductance (CVC) decreased more in DM+HC+CKD compared to CON, indicating an increased NO‐sensitivity (P=0.043, Figure).ConclusionIn swine with multiple co‐morbidities reduced bioavailability of NO appears to be compensated by increased sensitivity to NO, which is associated with maintained cGMP‐mediated vasodilator influence.Support or Funding InformationFunding: This study was supported by grants from the European Commission FP7‐Health‐2010 grant MEDIA‐261409, the Netherlands CardioVascular Research Initiative: an initiative with support of the Dutch Heart Foundation [CVON2014‐11 (RECONNECT)].

Nitrite oxidation kinetics of two Nitrospira strains: The quest for competition and ecological niche differentiation

Nitrite oxidation is an aerobic process of the nitrogen cycle in natural ecosystems, and is performed by nitrite-oxidizing bacteria (NOB). Also, nitrite oxidation is a rate-limiting step of nitrogen removal in wastewater treatment plants (WWTPs). Although Nitrospira is known as dominant NOB in WWTPs, information on their physiological properties and kinetic parameters is limited. Here, we report the kinetic parameters and inhibition of nitrite oxidation by free ammonia in pure cultures of Nitrospira sp. strain ND1 and Nitrospira japonica strain NJ1, which were previously isolated from activated sludge in a WWTP. The maximum nitrite uptake rate ( [Formula: see text] ) and the half-saturation constant for nitrite uptake ( [Formula: see text] ) of strains ND1 and NJ1 were 45 ± 7 and 31 ± 5 (μmol NO2-/mg protein/h), and 6 ± 1 and 10 ± 2 (μM NO2-), respectively. The [Formula: see text] and [Formula: see text] of two strains indicated that they adapt to low-nitrite-concentration environments like activated sludge. The half-saturation constants for oxygen uptake ( [Formula: see text] ) of the two strains were 4.0±2.5 and 2.6±1.1 (μM O2), respectively. The [Formula: see text] values of the two strains were lower than those of other NOB, suggesting that Nitrospira in activated sludge could oxidize nitrite in the hypoxic environments often found in the interiors of biofilms and flocs. The inhibition thresholds of the two strains by free ammonia were 0.85 and 4.3 (mg-NH3 l-1), respectively. Comparing the physiological properties of the two strains, we suggest that tolerance for free ammonia determines competition and partitioning into ecological niches among Nitrospira populations.

Electrocatalytic Activities of Graphene/Nile Blue Nanocomposite Toward Determination of Hydrogen Peroxide and Nitrite Ion

AbstractElectrocatalytic activities of graphene nanosheets/Nile blue nanocomposite, synthesized and adsorbed simultaneously on the glassy carbon (GC−GNs−NB) electrode, are investigated. The nanocomposite was characterized by ATR−FTIR, FESEM and voltammetry. Activity of the electrode toward reduction of H2O2 and oxidation of NO2− was studied electrochemically. Values of 1.95 and 0.730 mM are found for the Michaelis−Menten constant of the electrode toward H2O2 and NO2−, respectively. Wide dynamic response ranges were observed for the electrode, with DLs of 0.22 μM H2O2 and 1.1 μM NO2−. Effect of interferences was studied. The sensor was successfully tested for H2O2 and NO2− contents in real samples, respectively.

Nitrite reduction by Fe(II) associated with kaolinite

Interactions of iron (Fe) with the nitrogen (N) cycle have emerged and contain elements of abiotic and biological reactions. One such abiotic reaction which has received little study is the reactivity of NO2 − and Fe(II) associated with a major clay mineral, kaolinite. The main objective of this study was to evaluate the reactivity of NO2 − with Fe(II) added to kaolinite under anoxic conditions. Stirred batch reactivity experiments were carried out with 10 g L−1 kaolinite spiked with 25 and 100 µM Fe(II) at pH 6.45 in an anaerobic chamber. Approximately 500 µM NO2 − was added to initiate the reaction with Fe(II)-loaded kaolinite. The rate of nitrite removal from solution was 2.4-fold slower in the high Fe(II) treatment when compared with the low Fe(II) treatment. A large portion of the NO2 − removed from solution was confirmed to be reduced to N2O(g) in the Fe(II)-kaolinite slurries. However, NO2 − reduction was also noticed in the presence of kaolinite-alone and to somewhat lesser extent in the presence of dithionite-citrate-bicarbonate (DCB)-treated kaolinite. Chemical extractions coupled with infrared spectroscopy suggest that Fe(III) oxide mineral impurities and structural Fe(III) in kaolinite may participate in NO2 − removal from solution. Furthermore, a magnetite mineral was identified based on X-ray diffraction analysis of untreated kaolinite and DCB-treated kaolinite. Our findings reveal a novel pathway of NO2 − transformation in the environment in the presence of Fe(II) associated (sorbed and impurity) with kaolinite.

Children's respiratory health and oxidative potential of PM2.5: the PIAMA birth cohort study

IntroductionThe oxidative potential (OP) of particulate matter (PM) has been proposed as a health-relevant metric, but currently few epidemiological studies investigated associations of OP with health. Our main aim was...

Acute Exposure to Air Pollution Triggers Atrial Fibrillation

This study sought to evaluate the association of air pollution with the onset of atrial fibrillation (AF). Air pollution in general and more specifically particulate matter has been associated with cardiovascular events. Although ventricular arrhythmias are traditionally thought to convey the increased cardiovascular risk, AF may also contribute. Patients with dual chamber implantable cardioverter-defibrillators (ICDs) were enrolled and followed prospectively. The association of AF onset with air quality including ambient particulate matter <2.5 μm aerodynamic diameter (PM2.5), black carbon, sulfate, particle number, NO2, SO2, and O3 in the 24 h prior to the arrhythmia was examined utilizing a case-crossover analysis. In sensitivity analyses, associations with air pollution between 2 and 48 h prior to the AF were examined. Of 176 patients followed for an average of 1.9 years, 49 patients had 328 episodes of AF lasting ≥ 30 s. Positive but nonsignificant associations were found for PM2.5 in the prior 24 h, but stronger associations were found with shorter exposure windows. The odds of AF increased by 26% (95% confidence interval: 8% to 47%) for each 6.0 μg/m(3) increase in PM2.5 in the 2 h prior to the event (p = 0.004). The odds of AF were highest at the upper quartile of mean PM2.5. PM was associated with increased odds of AF onset within hours following exposure in patients with known cardiac disease. Air pollution is an acute trigger of AF, likely contributing to the pollution-associated adverse cardiac outcomes observed in epidemiological studies.

SGC in SMC acts as Nitrite Reductase leading to NO formation

Several heme proteins including hemoglobin and nitric oxide synthase (NOS) have been documented to serve as nitrite reductase under anoxia. Since sGC is also a heme protein and an important signaling biomolecule, we hypothesized that it may function as nitrite reductase in cultured smooth muscle cells. Millimolar levels of nitrite were required to detect cellular NO as measured by NO specific fluorescent dye (CuFL2E). However, in chemiluminescence analysis of cell lysates, addition of 400–600 μM NO2− was sufficient to detect measurable NO formation under anoxic conditions. This NO formation was inhibited with ODQ showing sGC in the cell lysate as the source of nitrite reduction. CO is a known activator of sGC and thus CO donor (50 μM CORM‐2) significantly activated nitrite reduction to NO. The cellular uptake of NO2− was studied using the AE‐1 inhibitor, DIDS and intracellular NO2− was measured by tri‐iodide assay. DIDS (300 μM) significantly inhibited NO2− uptake and showing that NO2− uses AE‐1 transport mechanism. These results demonstrate that sGC mediates NO2− reduction to form NO and that the AE‐1 channel is one of the pathways for NO2− entry into SMC. This work was supported by NIH grant SC1HL095101.

Electroanalytical properties of cytochrome c with direct electron transfer on graphene/gold nanoparticles chitosan modified glass carbon electrode

A nitrite (NO2−) sensor has been fabricated by immobilizing cytochrome c (Cyt c) on a graphene/gold nanoparticle-chitosan (Gra/Au NPs–Chit) modified glass carbon electrode (GCE). Graphene/gold nanoparticles (Gra/Au NPs) nanocomposite was prepared by dispersing graphene in an aqueous solution of β-cyclodextrin (β-CD) and hydrogen tetrachloroaurate and followed by NaBH4 reduction. An aliquot of Gra/Au NPs in a 0.50 wt% chitosan solution was drop-coated on the surface of a GCE to form a Gra/Au NPs–Chit/GCE which was subsequently adsorbed with Cyt c. The Cyt c–Gra/Au NPs–Chit/GCE shows a quasi-reversible cyclic voltammetric redox couple at a formal potential of −0.037 V (vs. SCE) in 0.10 M pH 7.0 phosphate buffer solution, suggesting that Gra/Au NPs–Chit film offers a biocompatible microenvironment for the Cyt c. It was found that the Cyt c–Gra/Au NPs–Chit sensor displays good electrocatalytic activity for NO2− oxidation at a relatively low working potential. The sensor possesses a linear response range of 10.0–420.0 μM NO2− with a correlation coefficient of 0.9989 and a sensitivity of 110.0 μA mM−1. The limit of detection is determined as 2.46 μM NO2− based on a signal-to-noise ratio of 3. The proposed sensor has been applied successfully to the determination of NO2− in spiked and real water samples.

Roles of pollution in the prevalence and exacerbations of allergic diseases in Asia

The prevalence of asthma and allergic diseases has been found to be increasingly rapidly, especially in developing countries. Environmental factors have been found to be important contributors to the manifestations of allergic diseases. Air pollution has been extensively studied in different regions of the world. The levels of ambient air pollutants in many Asian countries are very high when compared with those in developed Western countries. However, the prevalence of asthma was relatively low across many Asian countries. Many studies have clearly documented that environmental air pollution is an important factor resulting in exacerbations of asthma. In particular, levels of traffic-related pollutants are increasing rapidly across many Asian countries in parallel with the level of urbanization and economic development. The loss of protective factors associated with a rural environment will further contribute to the adverse effect on patients with allergic diseases such as asthma. In this review the roles of air pollution were examined in relation to the inception and exacerbations of allergic diseases in Asia.

Quantification of nitrite and nitrate in seawater by triethyloxonium tetrafluoroborate derivatization—Headspace SPME GC–MS

Triethyloxonium tetrafluoroborate derivatization combined with direct headspace (HS) or SPME-gas chromatography–mass spectrometry (GC–MS) is proposed here for the simultaneous determination of nitrite and nitrate in seawater at micromolar level after conversion to their corresponding volatile ethyl-esters (EtO-NO and EtO-NO2). Isotopically enriched nitrite [15N] and nitrate [15N] are employed as internal standards and for quantification purposes. HS-GC–MS provided instrumental detection limits of 0.07μM NO2− and 2μM NO3−. Validation of the methodology was achieved by determination of nitrite and nitrate in MOOS-1 (Seawater Certified Reference Material for Nutrients, NRC Canada), yielding results in excellent agreement with certified values. All critical aspects connected with the potential inter-conversion between nitrite and nitrate (less than 10%) were evaluated and corrected for by the use of the isotopically enriched internal standard.

Biphasic Behavior of Anammox Regulated by Nitrite and Nitrate in an Estuarine Sediment

The production of N2 gas via anammox was investigated in sediment slurries at in situ NO2- concentrations in the presence and absence of NO3-. With single enrichment above 10 microM 14NO2- or 14NO3- and 15NH4+, anammox activity was always linear (P < 0.05), in agreement with previous findings. In contrast, anammox exhibited a range of activity below 10 microM NO2- or NO3-, including an elevated response at lower concentrations. With 100 microM NO3-, no significant transient accumulation of NO2- could be measured, and the starting concentration of NO2- could therefore be regulated. With dual enrichment (1 to 20 microM NO2- plus 100 microM NO3-), there was a pronounced nonlinear response in anammox activity. Maximal activity occurred between 2 and 5 microM NO2-, but the amplitude of this peak varied across the study (November 2003 to June 2004). Anammox accounted for as much as 82% of the NO2- added at 1 microM in November 2003 but only for 15% in May 2004 and for 26 and 5% of the NO2- added at 5 microM for these two months, respectively. Decreasing the concentration of NO3- but holding NO2- at 5 microM decreased the significance of anammox as a sink for NO2-. The behavior of anammox was explored by use of a simple anammox-denitrification model, and the concept of a biphasic system for anammox in estuarine sediments is proposed. Overall, anammox is likely to be regulated by the availability of NO3- and NO2- and the relative size or activity of the anammox population.