Solubility Of NO Research Articles

Steady-state nitric oxide concentrations during denitrification.

Three species of denitrifying bacteria, Paracoccus denitrificans, Pseudomonas stutzeri strain JM300, and Achromobacter cycloclastes, were allowed to reduce nitrate or nitrite in anaerobic, closed vials while the equilibration of gases between aqueous and gas phases was facilitated by vigorous stirring. The gas phase was sampled and analyzed for NO with use of a chemiluminescence detector calibrated against bottled NO standards or against NO produced by the nitrite-iodide reaction. [NOaq] was inferred from [NOg] and the solubility of NO. NO was detected only during denitrification in amounts that, once established, did not change with time, were independent of the initial concentration of nitrate or nitrite, and were largely independent of cell concentration, at least when nitrate was the oxidant. The usual level of NO was promptly re-established following the addition of exogenous NO or following the loss of NO by sparging. The aforementioned properties are expected for a steady-state intermediate in denitrification. Steady-state [NOaq] ranged between 1 and 65 nM depending on species and conditions. Similar results were also obtained in a related experiment in which P. stutzeri strain ZoBell respired nitrite under growth conditions. The very low steady-state [NOaq] observed during denitrification imply that the maximum activity of nitric oxide reductase in vivo, if it could be realized, would be large relative to that for nitrite reductase. This circumstance allows NO to be an intermediate without reaching toxic steady-state levels.

Influence of the medium on the ionic dissociation of N 2O 4 and the kinetics of decomposition of N 2O 3 in aprotic solvents

Using the silver-silver chloride indicator electrode, the potentiometric technique has been employed to determine the ionic dissociation constant KiN2O4 corresponding to the reaction N2O4 ⇄ NO+ + NO−3 in aprotic media (nitromethane, propylene carbonate), taking into account the homolytic dissociation of N2O4 to NO2 in our calculation. The extent of N2O4 solvation has been correlated with the donor character of the solvent. We have generalized this property to reducible oxygenated nitrogen compounds such as NO+ and NO+2. In order explain the relative stability of N2O3 in sulfolane (despite the low solubility of NO in aprotic media), we have evaluated the rate constants for the reactions and in this solvent. Furthermore, the determination of enthalpies H°N2O3, H°N2O4 and H°NO2 corresponding to the heats of solution of N2O3, N2O4 and NO2, respectively, has allowed us to gain information concerning the effect of the medium on the molecular dissociations of N2O3.

Solubility of nitric oxide in aqueous and nonaqueous solvents

The solubility of NO in various solvents has been measured over a range of temperatures. The results are compared with the values predicted by various current theories of gas solubility.