Ab initio electronic structure calculations are used to explore the effect of nonneighboring positively charged groups on the ability of low-energy (<1 eV) electrons to directly attach to S-S sigma bonds in disulfides to effect bond cleavage. It is shown that, although direct vertical attachment to the sigma* orbital of an S-S sigma bond is endothermic, the stabilizing Coulomb potential produced in the region of the S-S bond by one or more distant positive groups can render the S-S sigma* anion state electronically stable. This stabilization, in turn, can make near vertical electron attachment exothermic. The focus of these model studies is to elucidate a proposed mechanism for bond rupture that may, in addition to other mechanisms, be operative in electron capture dissociation (ECD) experiments. The importance of these findings lies in the fact that a more complete understanding of how ECD takes place will allow workers to better interpret ECD fragmentation patterns observed in mass spectrometric studies of proteins and polypeptides.