Of the nine low-lying structures (shown in Figure ) computed for this cluster, six structures have the bisulfate moieties involved in a hydrogen bonding arrangement with each other. Bisulfate-bisulfate hydrogen bonding was found to be important to the structure of the dry (G) 0 (A) 4 (SA) 3 and larger ammonium bisulfate clusters. While the (G) 2 (A) 1 (SA) 2 is smaller than the (G) 0 (A) 4 (SA) 3 in terms of total number of cluster components, we hypothesize that the presence of the bulkier G encourages the formation of the bisulfate-bisulfate hydrogen bond. Kreinbihl and co-workers were able to identify and assign the out-of-plane OH bending transition characteristic of this type of hydrogen bonding. However, the region between 1300 -1400 cm -1 is rather complex here and prevents us from explicitly identifying the same spectral signature.