1.
Complex Interplay of Heme-Copper Oxidases with Nitrite and Nitric Oxide.
Chen, J, Xie, P, Huang, Y, Gao, H
International journal of molecular sciences. 2022;(2)
Abstract
Nitrite and nitric oxide (NO), two active and critical nitrogen oxides linking nitrate to dinitrogen gas in the broad nitrogen biogeochemical cycle, are capable of interacting with redox-sensitive proteins. The interactions of both with heme-copper oxidases (HCOs) serve as the foundation not only for the enzymatic interconversion of nitrogen oxides but also for the inhibitory activity. From extensive studies, we now know that NO interacts with HCOs in a rapid and reversible manner, either competing with oxygen or not. During interconversion, a partially reduced heme/copper center reduces the nitrite ion, producing NO with the heme serving as the reductant and the cupric ion providing a Lewis acid interaction with nitrite. The interaction may lead to the formation of either a relatively stable nitrosyl-derivative of the enzyme reduced or a more labile nitrite-derivative of the enzyme oxidized through two different pathways, resulting in enzyme inhibition. Although nitrite and NO show similar biochemical properties, a growing body of evidence suggests that they are largely treated as distinct molecules by bacterial cells. NO seemingly interacts with all hemoproteins indiscriminately, whereas nitrite shows high specificity to HCOs. Moreover, as biologically active molecules and signal molecules, nitrite and NO directly affect the activity of different enzymes and are perceived by completely different sensing systems, respectively, through which they are linked to different biological processes. Further attempts to reconcile this apparent contradiction could open up possible avenues for the application of these nitrogen oxides in a variety of fields, the pharmaceutical industry in particular.
2.
[Investigation of effect and process of nitric oxide removal in rotating drum biofilter coupled with absorption by Fe(II) (EDTA)].
Chen, J, Yang, X, Yu, JM, Jiang, YF, Chen, JM
Huan jing ke xue= Huanjing kexue. 2012;(2):539-44
Abstract
In order to accelerate the NO removal efficiency, a novel and effective system was developed for the complete treatment of NO from flue gases. The system features NO absorption by Fe(II) (EDTA) and biological denitrification in a rotating drum biofilter (RDB) so as to promote biological reduction. The experimental results show that a moderate amount of Fe(II) (EDTA) was added to the nutrient solution to improve the mass transfer efficiency of NO from gas to liquid, with the concomitant formation of nitrosyl complex Fe(II) (EDTA)-NO. Under the experimental conditions of rotational speed was at 0.5 r x min(-1), EBRT of 57.7 s, temperature was at 30 degrees C, pH was 7-8, with the increasing concentration of Fe(II) (EDTA) was from 0 mg x L(-1) to 500 mg x L(-1), the NO removal efficiency was improved from 61.1% to 97.6%, and the elimination capacity was from 16.2 g (m3 x h)(-1) to 26.7 g (m3 x h)(-1). In order to simulate the denitrifying process of waste gas containing NO by using RDB coupled with Fe(II) (EDTA) absorption, a tie-in equation of NO removal and the Fe(II) (EDTA) concentration added in RDB was established. The experimental NO removal efficiency change tendency agrees fairly with that predicted by the proposed equation.
3.
Dynamic model for nitric oxide removal by a rotating drum biofilter.
Chen, J, Jiang, Y, Chen, J, Sha, H, Zhang, W
Journal of hazardous materials. 2009;(2-3):1047-52
Abstract
To illustrate the process of nitric oxide (NO) denitrifying removal by a novel rotating drum biofilter (RDB), a dynamic model has been developed and further validated. Based on the mass component profile of NO at the gas-liquid interface combined with a Monod kinetic equation, the model was used to depict the mass transfer-reaction process of NO in RDB, focusing on the concentration distribution of NO in the gas, liquid, and biofilm phases. The NO distribution equation on the biofilm carrier was thereby achieved, as well as a dynamic model for NO elimination in the test system. Additionally, effects of operating parameters such as inlet NO concentration and empty-bed residence time on NO removal efficiency were evaluated through a sensitivity analysis of the model. The model was then modified taking the absorption of NO by nutrition liquid in the bottom of RDB into consideration. The results showed that the simulated data agreed well with the experimental data. The model made it possible to simulate a relatively high NO removal efficiency by RDB.