Multiple affinity removal system columns

Iodoacetamide (IAA), tris(2‐carboxyethyl) phosphine hydrochloride (TCEP), triethylammonium hydrogen carbonate buffer 1 M pH 8.5, sodium dodecyl sulfate, and β‐lactoglobulin (LACB) from bovine milk were purchased from Sigma (St. Louis, MO, USA). Formic acid (FA, 99%) and CH₃CN were from BDH (VWR International Ltd., Poole, UK). Hydroxylamine solution 50 wt% in H₂O (99.999%) was acquired from Aldrich (Milwaukee, WI, USA). H₂O (18.2 MΩ cm at 25°C) was obtained from a Milli‐Q apparatus (Millipore, Billerica, MA, USA). Trifluoroacetic acid Uvasol was sourced from Merck Millipore (Billerica, MA, USA). The 6‐plex isobaric tandem mass tags (TMTs) were purchased from Thermo Scientific (Rockford, IL, USA). Sequencing grade modified Lys‐C/trypsin was procured from Promega (Madison, WI, USA). For immuno‐affinity depletion of 14 abundant human proteins, multiple affinity removal system (MARS) columns, Buffer A, and Buffer B were obtained from Agilent Technologies (Wilmington, DE, USA). Oasis HLB cartridges (1cc, 30 mg) were acquired from Waters (Milford, MA, USA) and Strata‐X 33u Polymeric reversed‐phase (RP) and Strata‐X‐C 33u Polymeric strong cation‐exchange (SCX) solid‐phase extraction (SPE) cartridges (30 mg/1 mL) from Phenomenex (Torrance, CA, USA).