Isothermal shift assay was performed following similar procedure as with thermal shift assay. However, increasing indicated concentrations of the inhibitors (98 nM -200 µM) were used, which was incubated with either C-terminal or N-terminal of Hsp90 (5 µM) in the assay buffer (1X PBS, pH = 7.5) for 2 h. The samples were heated to 46°C after adding 6X SYPRO Orange dye (Sigma-Aldrich). Percent unfolding was calculated by normalizing to 100 % unfolding and comparison to vehicle control (DMSO).