Trichloroacetic acid solution 6.1n

Ammonium bicarbonate, dithiothreitol, trichloroacetic acid solution (6.1N), iodoacetamide, sodium deoxycholate, and sucrose were obtained from Sigma-Aldrich (St. Louis, MO). Sodium chloride, Optima grade acetone, Optima LC/MS grade water, acetonitrile, water with 0.1% (v/v) formic acid, and formic acid were purchased from Fisher Scientific (Fair Lawn, NJ). Imidazole and phenylmethylsulfonyl fluoride (PMSF) were from Acros Organics (NJ, USA), and EDTA was from Fluka Biochemika (Buchs, Switzerland). Anhydrous 2-propanol was acquired from Alfa Aesar (Ward Hill, MA). Bicinchoninic acid assay (BCA) and albumin standard were from Thermo Scientific (Rockford, IL). Frozen sequencing grade modified trypsin was purchased from Promega (Madison, WI). Synthetic ¹³C and ¹⁵N stable isotope-labeled (SIL heavy peptides) crude signature peptides were manufactured by ThermoFisher Scientific (> 99% isotopic enrichment according to the manufacturer) and were delivered in 50% acetonitrile and 0.1% trifluoroacetic acid.