The clusters discussed in this work will be referred to using the following nomenclature: shows mass spectra obtained by electrospraying two solutions with different ratios of G to ammonium sulfate (1:1, top; 1:3, bottom trace). Equal concentrations of G and ammonium sulfate result in an irregular pattern of clusters only at low m/z. Tripling the concentration of ammonium sulfate, however, results in a drastically different mass spectrum, wherein clusters are observed over a much larger m/z range in addition to a now apparent distribution pattern. A closer inspection of the peaks observed in the bottom trace reveals that the observed pattern corresponds to the formation of three types of clusters: ammonium bisulfate clusters, glycine bisulfate clusters, and mixed clusters with varying numbers of G, A, and SA. Inset in Figure is an example of all three cluster types, separated by 1 m/z. Ammonium bisulfate clusters are well-studied and here we have focused on some example clusters of the latter two types. A majority of the G containing clusters are singly charged. The number of SA molecules in each cluster is consistently one less than the sum of G and A per cluster, mirroring ammonium bisulfate clusters with the empirical formula (G) 0 (A) y (SA) z (where y = z+1). This similarity suggests that G behaves as a base. As shown in Figures , under similar conditions, we only observed anionic clusters over a small m/z range that were predominantly composed of SA and bisulfate only. Figures S3-S4 display the clusters observed in the bottom trace of Figure in terms of total number of G and SA per cluster.