Reactions between celastrol and thiol-containing agents and between celastrol and non-thiol small molecules. A: Absorption spectra of celastrol mixed with different agents. Celastrol was mixed with different small molecules in ratio of 1:2, the absorption spectra then detected. B-D: Mass spectrum analysis of the following agents or reactions: (B) celastrol; (C) the mixture of celastrol and DTT at a 1:2 molar ratio in DMSO; (D) celastrol and DTT reaction result with formic acid added (to save space, the detection patterns presented have been truncated. The non-truncated view can be found in this manuscript's additional file 2).