Comparing the collision-induced dissociation of trimethyl lysine+ and acetyl lysine-H+

Experimental and computational results are reported on the reaction dynamics taking place within the collision-induced dissociation (CID) of Nɛ, Nɛ, Nɛ-Trimethyl-L-lysine+ (TMe-lysine+) and Nɛ-acetyl-L-lysine-H+ (acetyl-lysine-H+). These common post-translational modifications result in a mass difference of only 0.036 Dalton. Resolving these two species directly requires a high-resolution instrument and they share several CID peaks. Nevertheless, the mechanisms observed are strikingly different, particularly at lower internal energies. Reactivity is higher for acetyl-lysine-H+, with decomposition initiated via losses at the N- and C-termini. In contrast, unmodified lysine and TMe-lysine+ exhibit mechanisms that involve an initial loss from the sidechain.