Secondary low-energy electrons are abundantly created during the early moments following the deposition of energy by radiation into cells. Here we show the ability of slow (<12 eV) electrons to effectively decompose gas-phase N-acetyl tryptophan (NAT) which can model a simple protein. The fragmentation of NAT, initiated via a resonant electron-molecule interaction exclusively at the peptide bridge, produces a large variety of negative species. The present findings contribute to the molecular description of the initial step in the radiation-induced damage.