Ieritano, ChristianCarr, Patrick J. J.Hasan, MoarajBurt, MichaelMarta, Rick A.Steinmetz, VincentFillion, EricMcMahon, Terrance B.Hopkins, W. Scott2020-10-262020-10-262016https://doi.org/10.1039/C5CP07414Bhttp://hdl.handle.net/10012/16473The proton-, lithium-, and sodium-bound cysteine dimers have been investigated in a joint computational and experimental infrared multiple photon dissociation (IRMPD) study. IRMPD spectra in the 1000–2000 cm−1 region show that protonation is localized on an amine group, and that intermolecular hydrogen bonding occurs between the protonated amine and the carbonyl oxygen of the neutral Cys moiety. Alkali-bound dimers adopt structures reminiscent of those observed for the monomeric Cys·Li+ and Cys·Na+ species. Calculations of the heavier Cys2·M+ (M = K, Rb or Cs) species suggest that these are significantly less strongly bound than the lighter (M = H, Li, or Na) dimers.enArticle