Ammonium bicarbonate buffer

LC‐MS grade acetonitrile, methanol, chloroform, and formic acid were purchased from Fisher Scientific (Fair Lawn, NJ). Standard human prothrombin, trichloroacetic acid (TCA), and trifluoroacetic acid (TFA) were purchased from Sigma‐Aldrich (St. Louis, MO). Isopropanol (IPA) was purchased from VWR DBH Chemicals. The protein quantification bicinchoninic acid assay kit was purchased from Pierce Biotechnology (Rockford, IL). Ammonium bicarbonate buffer (98% purity) was purchased from Acros Organics (Geel, Belgium). Human serum albumin, a surrogate protein matrix, was obtained from Calbiochem (Billerica, MA). Iodoacetamide, dithiothreitol, MS grade trypsin, and surrogate heavy peptides representing carboxy‐forms and des‐carboxy‐forms of prothrombin were purchased from Thermo Fisher Scientific (Rockford, IL).

Liquid chromatography tandem mass spectrometry (LC‐MS/MS) grade acetonitrile, methanol, chloroform, and formic acid were purchased from Fisher Scientific (Fair Lawn, NJ). Unconjugated and conjugated steroid standards were purchased from Cerilliant Corporation (Round Rock, TX) and Steraloid (Newport, RI; Supplementary Table S1). Recombinant human UGT2B7, UGT2B15, and UGT2B17 superosomes were purchased from Corning Life Science (Corning, NY), and dutasteride for the in vitro experiments was from Sigma Aldrich (St Louis, MO). Iodoacetamide, dithiothreitol, and pierce trypsin protease (MS grade) were purchased from Thermo Fisher Scientific (Rockford, IL). Ammonium bicarbonate buffer (98% purity) was purchased from Acros Organics (Geel, Belgium). Human serum albumin and bovine serum albumin (BSA) were obtained from Calbiochem (Billerica, MA) and Thermo Fisher Scientific, respectively. Surrogate peptides were produced by Thermo Fisher Scientific. UDPGA and MgCl₂ were purchased from Sigma‐Aldrich. Hepatocytes were provided gratis by Lonza (Walkersville, MD), hepatocyte thawing media (UCRM), hepatocyte plating media (UPCM), hepatocyte induction media (HIM) and hepatocyte quantification media (HQM) were procured from IVAL (Columbia, MD).