Short Review on the Chemistry of Nitrogen Fixation

All biochemical work on biological fixation of dinitrogen conducted during the last three decades strongly indicates that the formation of dinitrogen addition products with metal-complex enzymes and the low-temperature reduction of their dinitrogen ligand occupy a key position in that process. 

The enzymology and biochemistry of nitrogenases started only a few years before the first dinitrogen metal complex was discovered by Allen and Senoff in 1965. Cooperation and mutual encouragement increased when more and more results were found on both sides. Two iron-sulfur proteins are involved in the nitrogenase complex. The larger protein, the nitrogenase itself, consists of four subunits and has an 

The smaller protein has a molecular mass of 60000-70000 daltons. Extended X-ray absorption fine structure (EXAFS) studies show that it includes a single Fe4S4 cubane cluster (P-cluster) similar to that in ferredoxins, which are important for various electron transport chains in living organisms. The smaller protein in the nitrogenase system is a strongly reductive reductase that is obviously responsible for the transfer of electrons to the larger protein. 

The significance of the work of Kim and Rees for science in general is evident from the fact that in the book Chemistry Imagined, written by Roald Hoffmann, in a unique collaboration with artist Vivian Torrence (1993), nitrogen fixation and, in particular, the structure of the active site of FeMoco in nitrogenase (Fig. 3-3) is the subject of a particular essay. 

It seems fairly certain that the formation of ammonia in nitrogen fixation is based on four processes or groups of processes, namely (1) formation of a dinitro- 

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