Acetonitrile

Oxytocin was obtained from the Peptide Institute (Osaka, Japan). Liquid chromatography mass spectrometer (LC-MS)-grade water, acetonitrile (ACN), formic acid, trifluroacetic acid (TFA), and trichloroacetic acid (TCA) were purchased from Wako Chemicals (Tokyo, Japan). Stably-labelled Oxytocin [¹³C,¹⁵N]Oxytocin was synthesised using [¹³C₅,¹⁵N₁]-Pro₇ and [¹³C₆,¹⁵N₁]-Leu₈ (Scrum Co. Ltd., Tokyo, Japan), as described previously^{73 (link)}.

6-Bromopurine was purchased from Sigma-Aldrich/Merck (St. Louis, MO, USA). 6-Bromo-9-methylpurine and 6-bromo-7-methylpurine were synthesized as described previously (Okamura et al. 2009a (link), b (link)). Chloroform (CHCl₃, dehydrated) and super dehydrated solvents—acetone (ACT), acetonitrile (MeCN), ethyl acetate (AcOEt), N,N-dimethylformamide (DMF), tetrahydrofuran (THF), 1,4-dioxane (1,4-DO), diisopropyl ether (iPr₂O), toluene (Tol), and dichloromethane (DCM)—were purchased from FUJIFILM Wako Pure Chemical Corporation (Osaka, Japan). Methyl acetate (AcOMe, anhydrous) and 1,3-dioxane (1,3-DO) were purchased from Sigma-Aldrich/Merck. Methyl propionate (MP, special grade) was purchased from FUJIFILM Wako Pure Chemical Corporation. 2-Methyltetrahydrofuran (2-MeTHF, dehydrated) was purchased from KANTO CHEMICAL Co., INC (Tokyo, Japan). Aqueous 57% hydrogen iodide (HI) solution was purchased from FUJIFILM Wako Pure Chemical Corporation. Potassium Carbonate (K₂CO₃, guaranteed reagent) was purchased from FUJIFILM Wako Pure Chemical Corporation and was ground in a mortar into a fine powder, which was used for manual and automated syntheses. A 0.05–0.08 M solution of lithium aluminum hydride (LAH) in THF was prepared by diluting a 1.0 M solution of LAH in THF, which was purchased from Sigma-Aldrich/Merck.

Analytical grade colistin sulfate, netilmicin sulfate, 9-fluorenylmethyl chloroformate (FMOC-Cl), trichloroacetic acid, sodium hydroxide, acetone, sodium hydrogen carbonate, and boric acid, and HPLC grade methanol, acetonitrile, tetrahydrofuran, and distilled water were purchased from Wako Pure Chemical Industries, Ltd. (Osaka, Japan). The serum employed for quality control (QC) was purchased from Alfresa Pharma Corporation (Osaka, Japan).
Stock solutions of colistin sulfate (100 μg/mL) and netilmicin sulfate (5 μg/mL) internal standard were prepared by dissolving 1.0 and 0.05 mg of the respective substances in 10 mL of distilled water. A 100 mM FMOC-Cl stock solution was prepared by dissolving 258.7 mg of FMOC-Cl in 10 mL of acetonitrile. The carbonate buffer (1 wt%, pH 10) was prepared by dissolving the sodium hydrogen carbonate (1 g) in distilled water (100 mL) and the pH of the solution was adjusted to 10 using sodium hydroxide. All solutions were stable for at least 2months when stored in a refrigerator at 4 °C.

Quercetin, protoporphyrin IX (PpIX), dimethyl sulfoxide (DMSO) was purchased from Sigma-Aldrich, USA. Ethanol, superoxide dismutase (SOD), catalase, ethidium bromide, hypoxanthine, diethylenetriaminepentaacetic Acid (DTPA), trifluoroacetic acid, acetonitrile, iron(II) perchlorate, hydrogen peroxide, fluorescein, phosphoric acid, Dulbecco’s phosphate-buffered saline (D-PBS) were purchased from FUJIFILM Wako Pure Chemical Corporation., Japan. 3’-(p-aminophenyl) fluorescein (APF) was purchased from Sekisui Medical Co. Ltd., Japan. Dihydroethidium DHE was purchased from Invitrogen, CA. Compound libraries (Core library; for pilot screening) were provided by drug discovery initiative (DDI), the University of Tokyo (https://www.ddi.u-tokyo.ac.jp/en/). WST-8 was purchased from Dojin Laboratoies, Japan. Xanthine oxidase was purchased from Calbiochem (USA).

Ammonium bicarbonate, sodium deoxycholate (SDC), sodium N-lauroylsarcosinate (SLS), tris (hydroxymethyl) aminomethane (Tris), dithiothreitol (DTT), iodoacetamide (IAA), lysyl endopeptidase (Lys-C), ethyl acetate, acetonitrile (ACN), acetic acid, and trifluoroacetic acid (TFA) were obtained from FUJIFILM Wako. Protease inhibitor cocktail and phosphatase inhibitor cocktail 2 and 3 were obtained from Sigma-Aldrich. Trypsin was obtained from Promega. Empore disks for StageTips were obtained from GL Sciences.

Ethanol (Wako), acetonitrile (Wako), mEthanol (Wako), sulfuric acid (Wako), acetone (Wako), trifluoroacetate (Tokyo Chemical Industry), dimethyl sulfoxide (Wako), MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide), LPS and Griess reagent were all purchased from Sigma (St. Louis, MO, USA). An ELx 800 Universal Microplate Reader (BIO-TEK), VD-250R Freeze Dryer (TAITEC), US-105 Sonicator (SND), 5420 Centrifuge (IMOTO), R-300 Rotavapor (BUCHI), V-300 Vacuum Pump (BUCHI), High Performance Flash Chromatography (HPFC) system (Biotage AB), Medium Pressure Liquid Chromatography (MPLC) system (EPCLC, Yamazen), Preparative High Performance Liquid Chromatography (PHPLC) system (EPCLC, Yamazen), 1220 Infinity LC (Agilent Technologies), NMR spectrometer (Bruker DRX-600; Bruker Daltonics, Billerica MA, USA), Quadrupole time-of-flight (qTOF) mass spectrometer (Agilent Technologies, USA) and JASCO DIP-370 polarimeter (JASCO, Tokyo, Japan) were used.