Nitrogenase protein concentration

For the process in vivo flavodoxin is the external electron donor. For isolated nitrogenase, dithionite 8204 is traditionally used as electron donor. If dithionite is the external donor, the oxidized iron protein with 2MgADP (after the electron is transferred) then dissociates from the MoFe protein. This dissociation, which initially seemed necessary for enzyme function, is, however, apparently a result of the salt effect of dithionite, the concentration of which for effective electron transfer must be sufficiently large. 

Proteins are often unstable and may require special handling. For example, they may be especially sensitive to pH, temperature, or salt concentration, among other factors. Problems in handling a protein may become apparent only after considerable time and effort have been expended. For example, the investigation of nitrogenase, the enzyme that catalyzes the reduction of N2 to form NH3, was hindered for years until it was discovered that the enzyme s activity is destroyed by contact with 02. 

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