4.6.9. Peptide desalting

Enzymatic digestions were quenched by adding formic acid to a final concentration of 1%. Proteolytic peptides were desalted prior to LC‐MS/MS experiments. We used C18‐microcolumns (The Nest Group, MA, USA) following the manufacturer's instruction, or the AssayMAP Bravo platform using the peptide cleanup v2.0 protocol with C18 cartridges (Agilent, 5 μL bed volume). Peptides were eluted in 80% ACN, 0.1% TFA, dried on a Speevac, and dissolved in 0.1% formic acid or 0.1% TFA. Peptides generated by digestion with SDC protocol or on the S‐traps were directly analyzed by LC‐MS/MS without desalting.