Technical difficulties in studying membranes mean that only a few cross-membrane protein-to-protein signals are known. Both plant and human genomes contain thousands of membrane proteins whose functions remain mysterious. Similar techniques to identify membrane protein interactions have been used before to identify select membrane transporters. But Frommer's team developed a deeper process that was able to yield a greater diversity of results. The vast majority of the thousands of potential membrane protein-signaling protein interactions they found had never before been identified. The team's aim was to use their new protein interaction network to identify interactions important for protein-protein messaging and help assign possible functions to these "unknown" membrane proteins.