STED Nanoscopy in Living Cells Using Fluorogen Activating Proteins

We demonstrate the effectiveness of a genetically encoded malachite green (MG) binding fluorogen activating protein (FAP) for live cell stimulated emission depletion nanoscopy (STED). Both extracellular and intracellular FAPs were tested in living cells using fluorogens with either membrane expressed FAP or as an intracellular FAP-actin fusion. Structures with widths of 110-122 nm were observed. Depletion data, however, suggest a resolution of 70 nm with the given instrument.