Nitrogen cycle relevance

You mentioned the reaction between oxygen and nitrous oxide. Most environmental chemists pay attention to NO and NO2 as well as their interconversion, but little attention is paid to N2O. Does N2O have a part in the nitrogen cycle We are very curious about the fact that it is present uniformly in the troposphere at about 0.25 ppm. Is the reaction of oxygen and of direct relevance to the atmosphere ... 

Capone, D. G. (1991). Aspects of the marine nitrogen cycle with relevance to the dynamics of nitrous and nitric oxide. In Microbial Production and Consumption of Greenhouse Gases Methane, Nitrogen Oxides, and Halomethanes (Rogers, J. E., and Whitman, W. B., eds.). American Society of Microbiology, Washington, DC. pp. 255—275. 

For the purpose of this text on symbioses as they relate to the marine nitrogen cycle, we wiU first emphasize the more common open ocean diatom-diazotrophic associations (DDAs), then summarize the recent advances in our understanding of sponge-nitrifying microbial associations, and provide brief introductions to a few other relevant symbioses. In addition, we recommend, the chapter by O Neil and Capone (Chapter 21) for details on algal-animal symbioses of Coral Reefs as they relate to the nitrogen cycle. Chapter 4 by Carpenter and Capone on Nitrogen Fixation and Chapter 5 by Ward on Nitrification. 

Table 32.1 Enzyme activities relevant to marine nitrogen cycling... 

Capone D. G. (1991) Aspects of the marine nitrogen cycle with relevance to the dynamics of nitrous and nitric oxide. 

The interpretation of the factors mentioned above in the context of palaeodietary research is not straightforward a lack of nitrogen isotope data in relevant plant species makes the situation even more complicated. The observed variability in plants, even within ecosystems, is so extensive and so unpredictable that modelling of the behaviour of natural nitrogen abundances in plants is fraught with difficulties because there are no simple, universal laws governing the site-specific details of the N cycle, there will be no simple, universal laws of 8 N (in plants) (Handley and Raven 1992 Handley and Scrimgeour 1996). 

A template synthesis employing Ni(OAc)2, 2,5-dihydroxy-2,5-dimethyl-1,4-dithiane, and 3,3 -iminobis(propylamine) gave the water-soluble five-coordinate complex [Ni(495)], the crystal structure of which shows trigonal bipyramidal coordination of Ni11 with the central amine and terminal thiolates in plane and the two imino nitrogens in axial positions. Solvatochromism of the complex is interpreted in terms of S" H bonding, which may be of relevance to the catalytic cycle in hydrogenases.1341... 

Reduction of metal-nitrosyl complexes is a prominent subject in the redox chemistry of small nitrogenated molecules, most relevant to biochemistry and to natural nitrogen-redox cycles.11 MnNO+ complexes have low-energy LUMOs and undergo facile one-electron reduction, usually showing reversible CV waves associated with MNO+/MNO redox couples.4"-6 The MNO 6 complexes yield fairly stable MNO 7 species in solution, as evident from UV-vis, IR, and EPR. Some of the latter species release NO in the minute time scale alternatively, the [Fe(CN)5NO]3 and [Ru(NH3)5NO]2+ ions may lose cyanide or ammonia.4"-6 Some metallopor-phyrins also afford reversible conversion between MNO1 / MNO forms.21 The NiR enzymes release NO after nitrite coordination and reduction.11... 

The photolysis rate of atmospheric NO2 has been measured, and its dependences upon parameters such as the solar zenith angle and the amount of cloud cover have been evaluated.The photochemistry of small molecules containing sulphur, and its implications for the atmospheric S cycle have been discussed, as has the role of stratospheric reactive nitrogen as a source for species such as NO and HNO3 in the unpolluted troposphere. Ammonia concentrations have been calculated in the atmospheres of both Earth and Saturn the far-u.v. photolysis of mixtures of NH3 with methane results in the formation of amines and nitriles, and the relevance of these results to the evolution of primitive atmospheres has been discussed. ... 

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