Protonation postprotonation reaction

The simulation of the dynamics of protonation of bound Bromo Cresol Green, using Equations (37) and (38), failed to reproduce the observed dynamics as long as we assumed that the measured pK is a direct function of the forward and backward rates of proton transfer. This inadequacy led to the conclusion that for this case Koh kJk and provision must be made for a mechanism where the postprotonation reaction modulates the observed dynamic and equilibrium. 

The slower reaction, where the proton reacts with a ground-state molecular proton detector, widens the observation range. It can detect charge modulation of a protein, and the state of the water on an interface. The submicrosecond time resolution can discriminate proton exchange between donor-acceptor moieties located on the same structure from reaction with bulk proton. Similarly, it can resolve a complex proton-binding dynamics into initial and postprotonation events and it determines the contribution of each step to the overall measured equilibrium constants. 

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