We present herein a review of our work on the on-line electrochemical generation of mass tags toward cysteine residues in peptides and proteins. Taking advantage of the inherent electrochemical nature of electrospray generated from a microfabricated microspray emitter, selective probes for cysteine were developed and tested for on-line nonquantitative mass tagging of peptides and proteins. The nonquantitative aspect of the covalent tagging thus allows direct counting of free cysteines in the mass spectrum of a biomolecule through additional adduct peaks. Several substituted hydroquinones were investigated in terms of electrochemical properties, and their usefulness for on-line mass tagging during microspray experiments were assessed with L-cysteine, peptides, and intact proteins. Complementarily, numerical simulations were performed to properly understand the respective roles of mass transport, kinetics of electrochemical-chemical reactions, and design of the microspray emitter in the mass tagging overall efficiency. Finally, the on-line electrochemical tagging of cysteine residues was applied to the analysis of tryptic peptides of purified model proteins for protein identification through peptide mass fingerprinting. © 2004 American Society for Mass Spectrometry.
Roussel, C., Dayon, L., Lion, N., Rohner, T. C., Josserand, J., Rossier, J. S., … Girault, H. H. (2004). Generation of mass tags by the inherent electrochemistry of electrospray for protein mass spectrometry. Journal of the American Society for Mass Spectrometry, 15(12), 1767–1779. https://doi.org/10.1016/j.jasms.2004.08.006