On the role of short and strong hydrogen bonds on the mechanism of action of a model chymotrypsine active site.

The electronic properties of a chemical model that mimics the His-57...Asp-102 catalytic residues of alpha- chymotrypsine during the transition from normal hydrogen bond to short and strong hydrogen-bond regimes are presented. The results suggest that upon a global external stimulus induced by compression, the system response is the transfer of the nucleophilic reactivity from the model Asp-102 moiety toward the model His-57 fragment in the hydrogen-bonded complex. In this way, the catalytic effect may be consistently explained on the basis of a pair site reactivity model framed on the second-order static density response function.