DARTS assay was performed to assess protease protection of Hsp90 protein from thermolysin digestion after incubation of Hsp90i, as described previously. Briefly, 1 µg of recombinant Hsp90α was incubated on ice for 15 min with 25, 50 & 100 µM of 5b, NB, AUY922 and DMSO. After incubation the samples were treated with thermolysin (1:50 of protein) for 5 min. The reaction was halted by addition of 50 mM EDTA and later examined by immunoblot analysis.