 we combined single molecule fluorescence resonance energy transfer ( smfret ) with single particle tracking in live cells to detect the in vivo conformation of individual proteins . 
 we site - specifically labeled recombinant snare proteins with a fret donor and acceptor before microinjecting them into cultured cells . 
 we observed that individual proteins rapidly incorporated into folded complexes at the cell membrane , demonstrating the potential of this method to reveal dynamic interactions within cells . 
Supplementary Material