The cationic clusters discussed in this work were generated by electrospray ionization (ESI) of solutions containing 1 mM of glycine (Sigma-Aldrich, ACS reagent, ≥98.5%) and 1 mM of ammonium sulfate (Sigma-Aldrich, ACS reagent, ≥99%) in 75%/25% acetonitrile/water and 0.1% (v/v) formic acid. The ratio of glycine to the salt in the solutions was varied to control the composition of the clusters formed as discussed below.