Abstract

The electronic properties of a chemical model that mimics the His-57 ••• Asp-102 catalytic residues of a-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. © 2009 American Chemical Society.