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Nitrogen Monoxide (nitrogen + monoxide)
Selected AbstractsHigh Activity of Pt/AlPO4 Catalyst for Selective Catalytic Reduction of Nitrogen Monoxide by Propene in Excess Oxygen.CHEMINFORM, Issue 47 2003Ryuta Fujii Abstract For Abstract see ChemInform Abstract in Full Text. [source] Intermediates in the Autoxidation of Nitrogen MonoxideCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2009Benedikt Galliker Abstract ONOO. is an important intermediate in the autoxidation of nitrogen monoxide by dioxygen. A formerly unknown red isomer of N2O4, ONOONO (see figure), formed in 2-methylbutane at 113,K from nitrogen monoxide and dioxygen, is converted to O2NNO2 upon warming. We have identified two intermediates in the autoxidation of NO.: ONOO., which was detected by EPR spectroscopy at 295,K and atmospheric pressure in the gas phase, and ONOONO, a red substance produced at 113,K in 2-methylbutane. The red compound is diamagnetic and absorbs maximally at 500,nm. The ONOONO intermediate is unstable above the melting point of 2-methylbutane and rapidly converts to O2NNO2. From the semiquantitative determination of mole fractions present in the gas phase by EPR spectroscopy, we estimated the rate constants for the steps that lead to ONOO. and ONOONO, from the known overall rate constant of the autoxidation reaction, by assuming that a quasi-stationary mechanism applies. The rate constant for the rate-determining formation of ONOO. is about 3.1×10,18,cm3,molecule,1,s,1 (or 80,s,1 in mole fractions), the dissociation rate constant of ONOO. is about 6.5×103,s,1, and ONOONO is formed with a rate constant of k=7.7×10,14,cm3,molecule,1,s,1 (1.9×106,s,1 in mole fractions). From these constants, we estimate that the equilibrium constant for the formation of ONOO. from NO. and O2 (K) is 4.8×10,22,cm3,molecule,1 (1.2×10,2), and, therefore, ,G=+11.0,kJ,mol,1. In water, the Gibbs energy change is close to zero. The presence of ONOO. at steady-state concentrations under dioxygen excess may be important not only for reactions in the atmosphere, but especially for reactions in aerosols and biological environments, because the rate constant for formation in solution is higher than that in the gas phase, and, therefore, the half-life of ONOO. is longer. [source] Iron regulatory protein-independent regulation of ferritin synthesis by nitrogen monoxideFEBS JOURNAL, Issue 16 2006Marc Mikhael The discovery of iron-responsive elements (IREs), along with the identification of iron regulatory proteins (IRP1, IRP2), has provided a molecular basis for our current understanding of the remarkable post-transcriptional regulation of intracellular iron homeostasis. In iron-depleted conditions, IRPs bind to IREs present in the 5,-UTR of ferritin mRNA and the 3,-UTR of transferrin receptor (TfR) mRNA. Such binding blocks the translation of ferritin, the iron storage protein, and stabilizes TfR mRNA, whereas the opposite scenario develops when iron in the intracellular transit pool is plentiful. Nitrogen monoxide (commonly designated nitric oxide; NO), a gaseous molecule involved in numerous functions, is known to affect cellular iron metabolism via the IRP/IRE system. We previously demonstrated that the oxidized form of NO, NO+, causes IRP2 degradation that is associated with an increase in ferritin synthesis [Kim, S & Ponka, P (2002) Proc Natl Acad Sci USA99, 12214,12219]. Here we report that sodium nitroprusside (SNP), an NO+ donor, causes a dramatic and rapid increase in ferritin synthesis that initially occurs without changes in the RNA-binding activities of IRPs. Moreover, we demonstrate that the translational efficiency of ferritin mRNA is significantly higher in cells treated with SNP compared with those incubated with ferric ammonium citrate, an iron donor. Importantly, we also provide definitive evidence that the iron moiety of SNP is not responsible for such changes. These results indicate that SNP-mediated increase in ferritin synthesis is, in part, due to an IRP-independent and NO+ -dependent post-transcriptional, regulatory mechanism. [source] Potentialities of quantile regression to predict ozone concentrationsENVIRONMETRICS, Issue 2 2009S. I. V. Sousa Abstract This paper aims: (i) to analyse the influence of ozone precursors (both meteorological variables and pollutant concentrations) on ozone concentrations at different ozone levels; and (ii) to predict next day hourly ozone concentrations using a new approach based on quantile regression (QR). The performance of this model was compared with multiple linear regressions (MLR) for the three following periods: daylight, night time and all day. QR as proven to be an useful mathematical tool to evidence the heterogeneity of ozone predictor influences at different ozone levels. Such heterogeneity is generally hidden when an ordinary least square regression model is applied. The influence of previous concentrations of ozone and nitrogen monoxide on next day ozone concentrations was higher for lower quantiles. When QR was applied, the wind direction (WD) was found to be significant in the medium quantiles and the relative humidity (RH) in the higher quantiles. On the contrary, using the MLR models, both variables were not statistically significant. Moreover, QR allowed more efficient previsions of extreme values which are very useful once the forecasting of higher concentrations is fundamental to develop strategies for protecting the public health. Copyright © 2008 John Wiley & Sons, Ltd. [source] Iron regulatory protein-independent regulation of ferritin synthesis by nitrogen monoxideFEBS JOURNAL, Issue 16 2006Marc Mikhael The discovery of iron-responsive elements (IREs), along with the identification of iron regulatory proteins (IRP1, IRP2), has provided a molecular basis for our current understanding of the remarkable post-transcriptional regulation of intracellular iron homeostasis. In iron-depleted conditions, IRPs bind to IREs present in the 5,-UTR of ferritin mRNA and the 3,-UTR of transferrin receptor (TfR) mRNA. Such binding blocks the translation of ferritin, the iron storage protein, and stabilizes TfR mRNA, whereas the opposite scenario develops when iron in the intracellular transit pool is plentiful. Nitrogen monoxide (commonly designated nitric oxide; NO), a gaseous molecule involved in numerous functions, is known to affect cellular iron metabolism via the IRP/IRE system. We previously demonstrated that the oxidized form of NO, NO+, causes IRP2 degradation that is associated with an increase in ferritin synthesis [Kim, S & Ponka, P (2002) Proc Natl Acad Sci USA99, 12214,12219]. Here we report that sodium nitroprusside (SNP), an NO+ donor, causes a dramatic and rapid increase in ferritin synthesis that initially occurs without changes in the RNA-binding activities of IRPs. Moreover, we demonstrate that the translational efficiency of ferritin mRNA is significantly higher in cells treated with SNP compared with those incubated with ferric ammonium citrate, an iron donor. Importantly, we also provide definitive evidence that the iron moiety of SNP is not responsible for such changes. These results indicate that SNP-mediated increase in ferritin synthesis is, in part, due to an IRP-independent and NO+ -dependent post-transcriptional, regulatory mechanism. [source] Bioprocesses for the removal of nitrogen oxides from polluted airJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2005Yaomin Jin Abstract Nitrogen oxides (NOx) of environmental concern are nitrogen monoxide (NO) and nitrogen dioxide (NO2). They are hazardous air pollutants that lead to the formation of acid rain and tropospheric ozone. Both pollutants are usually present simultaneously and are, therefore, called NOx. Another compound is N2O which is found in the stratosphere where it plays a role in the greenhouse effect. Concern for environmental and health issues coupled with stringent NOx emission standards generates a need for the development of efficient low-cost NOx abatement technologies. Under such circumstances, it becomes mandatory for each NOx-emitting industry or facility to opt for proper NOx control measures. Several techniques are available to control NOx emissions: selective catalytic reduction (SCR), selective non-catalytic reduction (SNCR), adsorption, scrubbing, and biological methods. Each process offers specific advantages and limitations. Since bioprocesses present many advantages over conventional technologies for flue gas cleaning, a lot of interest has recently been shown for these processes. This article reviews the major characteristics of conventional non-biological technologies and recent advances in the biological removal of NOx from flue gases based on the catalytic activity of either eucaryotes or procaryotes, ie nitrification, denitrification, the use of microalgae, and a combined physicochemical and biological process (BioDeNOx). Relatively uncomplicated design and simple operation and maintenance requirements make biological removal a good option for the control of NOx emissions in stationary sources. Copyright © 2005 Society of Chemical Industry [source] Intermediates in the Autoxidation of Nitrogen MonoxideCHEMISTRY - A EUROPEAN JOURNAL, Issue 25 2009Benedikt Galliker Abstract ONOO. is an important intermediate in the autoxidation of nitrogen monoxide by dioxygen. A formerly unknown red isomer of N2O4, ONOONO (see figure), formed in 2-methylbutane at 113,K from nitrogen monoxide and dioxygen, is converted to O2NNO2 upon warming. We have identified two intermediates in the autoxidation of NO.: ONOO., which was detected by EPR spectroscopy at 295,K and atmospheric pressure in the gas phase, and ONOONO, a red substance produced at 113,K in 2-methylbutane. The red compound is diamagnetic and absorbs maximally at 500,nm. The ONOONO intermediate is unstable above the melting point of 2-methylbutane and rapidly converts to O2NNO2. From the semiquantitative determination of mole fractions present in the gas phase by EPR spectroscopy, we estimated the rate constants for the steps that lead to ONOO. and ONOONO, from the known overall rate constant of the autoxidation reaction, by assuming that a quasi-stationary mechanism applies. The rate constant for the rate-determining formation of ONOO. is about 3.1×10,18,cm3,molecule,1,s,1 (or 80,s,1 in mole fractions), the dissociation rate constant of ONOO. is about 6.5×103,s,1, and ONOONO is formed with a rate constant of k=7.7×10,14,cm3,molecule,1,s,1 (1.9×106,s,1 in mole fractions). From these constants, we estimate that the equilibrium constant for the formation of ONOO. from NO. and O2 (K) is 4.8×10,22,cm3,molecule,1 (1.2×10,2), and, therefore, ,G=+11.0,kJ,mol,1. In water, the Gibbs energy change is close to zero. The presence of ONOO. at steady-state concentrations under dioxygen excess may be important not only for reactions in the atmosphere, but especially for reactions in aerosols and biological environments, because the rate constant for formation in solution is higher than that in the gas phase, and, therefore, the half-life of ONOO. is longer. [source] | ||||||||||