Table 1. Summary of thiol-based reactivity reporters.

Adapted from NIH Assay Guidance Manual under Creative Commons AttrCoulter Avanti J-26XPibution-NonCommercial-ShareAlike 3.0 Unported license (CC BY-NC-SA 3.0) (Dahlin et al., 2015a).

Reporter	Chemical structure	Potential advantages and formats	Other comments and potential disadvantages	References
Glutathione (GSH)		Inexpensive Commercially available Widely used Biologically relevant Not UV-active HPLC-, fluorescence-based methods	Non-proteinaceous Prone to oxidation	(Dahlin et al., 2015c)
Coenzyme A (CoA)		Biologically relevant Commercially available UV-active HPLC-, fluorescence-based methods	More expensive relative to GSH Higher MW Non-proteinaceous	(Dahlin et al., 2015c)
Cysteamine		Inexpensive Commercially available HPLC-, NMR-based methods (1H)	Non-proteinaceous Small MW changes with adducts Prone to oxidation	(Arsovska et al., 2014; Olson et al., 2013)
Dithiothreotol (DTT)		Inexpensive Commercially available HPLC-based methods	Short aqueous half-life (oxidizes) Non-proteinaceous	(Bowers et al., 2010)
L-cysteine		Inexpensive Commercially available HPLC-based methods	Non-proteinaceous
MTSI		HTS capability Fluorescence-based method HPLC-based method also available	Non-proteinaceous Not commercially available O2-sensitive Reporter can form self-dimers	(McCallum et al., 2013)
Peptides	–	Protein-like (amino acid-based) HPLC-based Synthetically accessible and customizable	Non-proteinaceous?	(Wei et al., 2014)
Proteins	–	Some proteins amenable to intact ionization Enzyme digests can help determine specific adduct sites LC-MS based methods	Low-throughput Purified protein requirements Instrumentation and expertise requirements Not every peptide/adduct ionizable	(Dahlin et al., 2015c)
ALARM NMR	–	Protein-based May identify non-GSH-reactive compounds Provides information about protein conformation changes Stable protein (oxidation, RT) Adaptable to protein MS	Cost Instrumentation requirements Qualitative readout in current form	(Dahlin et al., 2015b; Dahlin et al., 2015c; Huth et al., 2005; Huth et al., 2007)