With the DZE probes in hand, we first evaluated if a carbonic anhydrase(CA)-DZE-desthiobiotin trifunctional probe (sulfa-DZE, 15) can label free CA in an electrochemically dependent and selective manner. Accordingly, 15 was incubated in the presence of 1:1 CA and bovine serum albumin (BSA) in PBS followed by 1-minute electrolysis (Figure ). Visualization via western blot revealed desthiobiotinylation of CA in an electrochemically dependent manner with highly selective labeling of CA over BSA (Figure and Figure ). Importantly, this biotinylation effect could be competed away with free CA-inhibitor.