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The preferred nitrogen electron acceptors in order of most to least thermodynamically favorable include nitrate (NO 3 −), nitrite (NO 2 −), nitric oxide (NO), nitrous oxide (N 2 O) finally resulting in the production of dinitrogen (N 2) completing the nitrogen cycle.
The copper-containing enzyme nitrite reductase (CuNIR) catalyzes the 1-electron reduction of nitrite to nitric oxide. The proposed mechanism entails the protonation of a κ 2O,O-NO 2-Cu(I) complex. This protonation induces cleavage of an N–O bond, giving a HO–Cu–ON center, which features a nitric oxide ligand O-bonded to Cu(II) (an ...
Electron affinity can be defined in two equivalent ways. First, as the energy that is released by adding an electron to an isolated gaseous atom. The second (reverse) definition is that electron affinity is the energy required to remove an electron from a singly charged gaseous negative ion.
Nitrate, acting as an oxidant, is therefore reduced in a succession of four reactions performed by the enzymes nitrate, nitrite, nitric-oxide, and nitrous oxide reductases. [2] The pathway ultimately yields reduced molecular nitrogen (N 2), as well as, when the reaction does not reach completion, the intermediate species nitrous oxide (N 2 O).
Hydrated copper nitrate is prepared by treating copper metal or its oxide with nitric acid: [7] Cu + 4 HNO 3 → Cu(NO 3) 2 + 2 H 2 O + 2 NO 2. The same salts can be prepared treating copper metal with an aqueous solution of silver nitrate. That reaction illustrates the ability of copper metal to reduce silver ions.
The transformation from nitrate to nitrite is performed by nitrate reductase (Nar) NO 3 − + 2 H + + 2 e − → NO 2 − + H 2 O. Nitrite reductase (Nir) then converts nitrite into nitric oxide 2 NO 2 − + 4 H + + 2 e − → 2 NO + 2 H 2 O. Nitric oxide reductase (Nor) then converts nitric oxide into nitrous oxide 2 NO + 2 H + + 2 e − → ...
Nitric oxide reductase is in Class 1, therefore it is an oxidoreductases. [5] Figure 1. The Nitrogen Cycle. Nitric oxide (NO) and nitrous oxide (N 2 O) are intermediates in the denitrification of nitrate (NO 3 −) to nitrogen gas (N 2). Nitric oxide reductase reduces NO to N 2 O.
These complexes are isoelectronic and, incidentally, both obey the 18-electron rule. The formal description of nitric oxide as NO + does not match certain measureable and calculated properties. In an alternative description, nitric oxide serves as a 3-electron donor, and the metal-nitrogen interaction is a triple bond. linear and bent M-NO bonds