Nitrogen biological chemistry

Most of biological chemistry can be understood in terms of simple ball and stick models. The chemistry of nitric oxide and related oxides is more intimidating because its patterns of bonding depend strongly on quantum mechanics and molecular orbital theory. But the basics can be grasped by comparison to other molecules and a simple consideration of where nitrogen sits in the periodic table. 

Averill, B. A., and Tiedje, J. M. (1990). Abstract INOR 103, Symposium on Inorganic and Biological Chemistry of Nitrogen, 200th ACS National Meeting American Chemical Society, Washington, D. C., Aug. 26-31. 

Fig. 4.—Quantitative, Precipitin Curve of Dextran B-1355-S with Con A.309 [The total amount of dextran in the precipitate is also illustrated. Con A, 42 tg of nitrogen. (Reproduced by permission of the Journal of Biological Chemistry.)]...

I should like to thank my colleagues in the Unit, later the Nitrogen Fixation Laboratory, and now part of the Department of Biological Chemistry at the John Innes Centre in Norwich, who have helped me in this research and some of whose results I have presented here. Special thanks, in reverse order of age, go to Marcus Durrant, Dave Evans, Chris Pickett, David Hughes and Ray Richards. 

McLaren, A. D., Peterson, G. H., Physical Chemistry and Biological Chemistry of Clay Mineral-Organic Nitrogen Complexes in Soil Nitrogen, Agron, J, (1965) 10, 259-284. 

An excellent discussion of both the physical and biological chemistry of clay mineral—organic nitrogen complexes has been presented by McLaren and Peterson... 

Mikkelsen, R.B. and Wardman, P., Biological chemistry of reactive oxygen and nitrogen and radiation-induced signal transduction mechanisms. Oncogene, 11 (37), 5734,2003. 

It is seen that a complete account of the biochemical catalysts would have to be a veritable treatise on biological chemistry and physiology. The author has limited his task to a less comprehensive plan, and has occupied himself exclusively with the catalysts for nitrogenous substances. The chemists will... 

As for nitrogen, biogenic redox processes are essential to convert sulfur from its largest oxidation state +VI (sulfate) to its lowest -II (sulfide). Sulfate is the most stable compound in the atmosphere once it has been produced there is no abiotic reduction possible in the climate system. Organisms need sulfur in the form of thiols RSH (simple thiols are called mercaptanes) and sulfides R2S. Thiols are (similar to alcohol ROH) weak acids (but much stronger). Thiols are easy oxidized into sulfides (this reaction is the main function in biological chemistry Fig. 5.25), thereby thiols provide hydrogen for the reduction of other molecules (the dissociated form RS" acts as an electron donor) ... 

As fully discussed in "Connections to Biological Chemistry The Unique Structure of Amide Bonds" in Section 18.2, the carbon and nitrogen of an amide are actually planar with approximately 120 bond angles about each because of resonance... 

Pyridoxal phosphate (PLP) is at the heart of chemistry conducted by a number of enzymes. Many of us know the coenzyme pyridoxal phosphate by the closely related vitamin from which it is derived in our diet—pyridoxine, or vitamin 06. Wheat is a good dietary source of vitamin 06. Although pyridoxal phosphate (see below and the model) is a member of the aldehyde family, when it is involved in biological chemistry, it often contains the closely related functional group with a carbon-nitrogen double bond, the imine group. 

RITTENBURG D., KESTON A.S., ROSEBURY F. and SCHOENHEIMER R. 1939. Studies on protein metabolism. II. The determination of nitrogen isotopes in organic compounds. Journal of Biological Chemistry, 127, 291-299. 

In this chapter, we focus predominantly on recent experimental and theoretical work that specifically pertains to modeling aspects of biological nitrogen fixation. As numerous thorough and recent reviews have already been written on this topic [2, 4, 6, 13-15], and as there are reviews that also cover inorganic nitrogen activation chemistry with a more broadly defined scope [15, 16], we will... 

Reactions. The chemistry of the /V-nitrosamines is extensive and will be only summarized here (8,35,42). Most of the reactions of the nitrosamines, with respect to thek biological or environmental behavior, involve one of two main reactive centers, either the nitroso group itself or the C—H bonds adjacent (a) to the amine nitrogen. The nitroso group can be removed readily by a reaction which is essentially the reverse of the nitrosation reaction, or by oxidation or reduction (68,69). 

Heterocyclic amines are compounds that contain one or more nitrogen atoms as part of a ring. Saturated heterocyclic amines usually have the same chemistry as their open-chain analogs, but unsaturated heterocycles such as pyrrole, imidazole, pyridine, and pyrimidine are aromatic. All four are unusually stable, and all undergo aromatic substitution on reaction with electrophiles. Pyrrole is nonbasic because its nitrogen lone-pair electrons are part of the aromatic it system. Fused-ring heterocycles such as quinoline, isoquinoline, indole, and purine are also commonly found in biological molecules. 

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