Ammonium bicarbonate

2-bromoethylamine hydrobromide, TRIS hydrochloride, trypsin, α-cyano-4-hydroxycinnamic acid (CHCA), acetylated cysteine (Ac-C), and acetic anhydride were purchased from Sigma (St. Louis, MO, USA). Glu-C was from Promega (Madison, WI, USA). Potassium phosphate was acquired from JT Baker (Phillipsburg, NJ, USA) and ammonium bicarbonate was from Mallinckrodt Chemicals (Phillipsburg, NJ, USA). Concentrated sodium hydroxide was obtained from VWR Analytical (Radnor, PA, USA) and dithiothreitol was purchased from Bio-Rad (Hercules, CA, USA). Genentech (South San Francisco, CA, USA) provided the antibody, rituximab. Fmoc-Arg(Ptf) Wang resin and Fmoc-Cys(Trt)-OH were from Midwest Biotech (Fishers, IN, USA).

Toyopearl AF-Formyl-650M resin was from Tosoh Bioscience (King of Prussia, PA, USA). Wheat germ agglutinin (WGA) was purchased from Vector Laboratories (Burlingame, CA, USA). Stainless steel columns (2×250 mm) and the Gemini C18 column were obtained from Phenomenex (Torrance, CA, USA). Ovomucoid (type III-O, free of ovoinhibitor), trypsin (TPCK treated), PNGase F, chloroform, NaOH beads (97% purity), iodomethane, 2-mercaptoethanol, dithiothreitol, iodoacetamide, trizma base, and sodium cyanoborohydride (NaCNBH₃) were all purchased from Sigma-Aldrich (St. Louis, MO, USA). Water and acetonitrile (ACN) were obtained from EMD Chemicals (Darmstadt, Germany). Formic acid was from Alfa Aesar (Ward Mill, MA, USA). Trifluoroacetic acid (TFA), dimethylformamide (DMF), urea, ammonium bicarbonate, sodium chloride, magnesium chloride, and calcium chloride were all from Mallinckrodt Pharmaceuticals (St. Louis, MO, USA). C18 Zip-tips were from Agilent Technologies (Santa Clara, CA, USA). C18 Sep-Pak cartridges were from Waters (Milford, MA, USA). Empty spin columns were purchased from Harvard Apparatus (Holliston, MA, USA).