Maximum absorption wavelengths λmax for σ* ← σ vertical transition of peptidic disulfide radical anions of increasing complexity were investigated by means of time-dependent density functional theory. Values among a representative set of 17 two-cysteinyl peptides range between 385 and 624 nm (TD-BH&HLYP/DZP++//MP2/DZP++:HF/6-31G* level of theory). This considerable spread contrasts with the usually admitted value of ca. 400−450 nm typically ascribed to two-center three-electron bonds. It is traced back to the large range of equilibrium intersulfur distances d, with values comprised between 2.73 and 3.19 Å. More quantitatively, blue- and red-shifts follow a near-linear regime (slope of 46 nm per 0.1 Å). They can be mapped onto a relaxed scan of l,l-cystine taken as a prototypical system λmaxref = 436 nm, 2.79 Å. This result could assist future radioprotectants rational design, with disulfide-linking arcs of controlled geometry. Meanwhile, the presence of a secondary structure motif such as an α-helix does not affect the UV−vis transition.Keywords (keywords): three-electron two-center bonds; absorption; TD-DFT; spectral tuning; peptide