PCET in Nitrite Reductase

Dissimilatory nitrite reductases (NiR) play a pivotal role in the anaerobic respiration cascade of denitrifying bacteria, archaea and fungi by catalysing the first committed step of the pathway.The net reaction of NiR yields the conversion of nitrite (N02 ) into gaseous nitric oxide (NO) and water (H2O) (eqn (3.12) ref. 207)  

The TlCu to T2Cu ET in NiR has been extensively analysed by pulse radiolysis using the colour change of the blue TlCu (8500 6.3 mM cm per NiR trimer) with observed ET rate constants (A EXobs) ranging from 150 s to 2000 Due to the absence of any systematic analysis 

The presented case study on inter-Cu ET in 4xNiR demonstrates the experimental challenges associated with PCET reactions. The existence of multiple pathways renders any mathematical analysis rather complex, especially if only one macroscopic parameter - as in this case EXobs is experimentally accessible. All attempts to employ the pH indicator phenol red in the laser experiments to obtain rate constants of the PT steps (kpxobs) failed, which we attribute to potential photo-reduction and/or photo-degradation processes of the dye. Due to 

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