We first sought to investigate whether SSAs 1-3 could mediate cation transport in synthetic phospholipid vesicle systems. Based on literature precedent, we initially explored a pH gradient assay using the pH sensitive fluorescent dye HPTS, which is commonly used to assess potential M + /H + antiport (or M + /OH -symport) processes, and can be adapted to examine M + uniport processes in the presence of a proton carrier such as carbonyl cyanide 3-chlorophenylhydrazone (CCCP). However, we discovered that the intrinsic fluorescence of SSA 2 was greatly enhanced in the presence of CCCP under the conditions of our transport assay (Section S2.2). This interfered with the detection of the fluorescence emission of the HPTS dye and precluded our use of this assay. We next attempted a modified K + /Na + antiport assay, inspired by recent work from Gale, Sessler and Shin, which uses a potassium selective electrode to monitor K + efflux from phospholipid vesicles. However, we found that the TBA counter cation of SSAs 1-3 caused interference with the potassium electrode (see Section S2.3), with the addition of a solution of TBA nitrate producing a similar response to all of the SSAs studied.