Förster resonance energy transfer (FRET) can be measured in expanded samples. HeLa cells were incubated with TFSM 1 for 24 h in the presence of 1% FBS. Then, the compound was removed, and cells were treated with 2.5 g/ml bacterial sphingomyelinase (bSMase) or left untreated for 24 h. Samples were fixed, stained, and expanded as described in ( a ) and analyzed via acceptor photobleaching to determine FRET efficiency. n = 4.
