Covalent modifications of BSA by disulfide prochelators as monitored by native mass spectrometry. Spectra are shown on the left with annotated charge states. Corresponding deconvolved mass distributions are shown on the right. Solutions of BSA (1.0 μM) in aqueous ammonium acetate (0.2 M, pH 6.8) were incubated in the presence of prochelators (244mTC-S)2 (panels a, b), (IT1-S)2 (c, d), (IT2-S)2 (e, f), or control thioether TE1 (g, h). The concentration of all tested compounds was 10 μM, and the incubations were conducted at room temperature for 24 h.