Investigation of the interaction of nitrogen-fixing complex of Azotobacter vinelandii with inhibitors of fixation N₂ by the EPR method

Reagents the action of which is directed preferentially at the nitrogen activation centre (N₂, CO, diazobenzosulphonic acid) produced minor changes in the EPR spectrum in the region g = 1·94 and g = 2·01. Nitric oxide completely blocking electron transport leads to the transformation of the EPR signal with g = 1·94 and g = 2·01 into a new signal with g = 2·03 the appearance of which indicates the presence in the electron activating centre of the complex of non-haeme iron bound to the cysteine groups. In the enzymatic activity of the nitrogen-fixing complex a special role is played by the SH groups not directly entering the system of non-haeme iron.