For the forward direction (deprotonation), a site of a polyelectrolyte undergoes change from 0 to -q, where q is the proton charge, while simultaneously, a hydronium ion is "created" at a random position inside the cell. Conversely, in the backward reaction (protonation move), a negatively charged site is neutralized and simultaneously, one random hydronium ion is deleted from the cell. The simulation starts with a charge neutral system, so that for each negative site of polyelectrolyte, there is a hydronium ion present in the bulk of the cell.