Iodomethane

Reagents of analytical grade were used as received from their commercial sources. Benzyl chloride was obtained from ACROS Organics (Morris Plains, NJ, USA), potassium hydroxide from Riendemann Schmidt (Kajang, Malaysia), carbon disulfide from Fisher Scientific (Chino, CA, USA) and copper (II) acetate from R&M Chemicals (Essex, UK). Hydrazine hydrate, iodomethane, glyoxal, 2,3-hexanedione, 2,3-heptanedione, 2,3-pentanedione, 2,3-butanedione and copper (II) chloride were obtained from Merck (Darmstadt, Germany). Absolute ethanol, 95% ethanol, dimethyl sulfoxide, acetone and dimethylformamide were obtained from RCI Labscan (Bangkok, Thailand). Elemental analysis was conducted via a Vario MACRO CUBE CHNS analyser (Germany), while IR spectra were recorded using a PerkinElmer FTIR spectrophotometer (Waltham, MA, USA). Melting points were measured using an Electrothermal IA9100 melting point apparatus (Essex, UK).
¹H NMR spectra were obtained via a Bruker FT-NMR 300 MHz (Germany). TLC was performed via 60F aluminium silica gel aluminium plates with a 254 nm fluorescent indicator from Merck (Darmstadt, Germany). UV-Vis spectroscopy was performed via a Biochrom UltroSpec 8000 spectrophotometer (Cambridge, UK).

Trifluoroacetic acid (TFA), ammonium bicarbonate (ABC), formic acid (FA), dithiothreitol (DTT), iodoacetamide (IAM), and Tween 20 were purchased from Sigma-Aldrich (St. Louis, MO, USA). Sodium hydroxide, DMSO, iodomethane and trichloromethane were purchased from Merck Millipore (Darmstadt, Germany). Trypsin was purchased from Promega (15,664 unit/mg, Sequence Grade, WI, USA). Acrylamide, SDS and TEMED were obtained from Bio-Rad (Hercules, CA, USA). Acetonitrile (ACN) was purchased from J.T. Baker (Phillipsburg, NJ, USA). Deionized water was generated with a Simplicity Ultrapure Water System (Millipore, Burlington, MA, USA) with a measured value of 18 MΩ.

PPFSt was prepared as described in our earlier study [13 ]. F6-PBI was purchased from Yanjin Technology, Shenzhen, China. Sulfuric acid, methyl ethyl ketone, potassium hydroxide, 0.1 N standard hydrochloric acid and sodium chloride were purchased from Carl Roth GmbH, Karlsruhe, Germany. N-methyl-2-pyrrolidone (NMP) and diethyl ether were obtained from Sigma-Aldrich, Munich, Germany. N,N-dimethylacetamide was purchased from Acros Organics, Darmstadt, Germany. Sulfuric acid was purchased from VWR International, Bruchsal, Germany. 1-(2-dimethylaminoethyl)-5-mercaptotetrazole (DMAEMTZ) and triethylamine were purchased from TCI Chemicals, Eschborn, Germany. Iodomethane was purchased from Merck, Darmstadt, Germany. The vanadium electrolyte solution (1.6 M vanadium in 30% Sulfuric acid: 50% VO²⁺ and 50% V³⁺) was supplied by RIVA GmbH Batteries, Backnang, Germany. Nafion^®212 (Nafion) was purchased from Ion Power GmbH, Munich, Germany.

Trypsin, sodium dihydrogen phosphate monohydrate, di-sodium hydrogen phosphate dihydrate, 1,4-dithioerythritol (DTE), 2-iodoacetamide (IAA), sodium borohydride, Dowex 50WX8 ion exchange resins, sodium hydroxide (NaOH), iodomethane, sDHB (9:1 mixture of 2,5-dihydroxybenzoic acid and 2-hydroxy-5-methoxy benzoic acid) and dextran were purchased from Merck (Taufkirchen, Germany). Acetonitrile (ACN) and anhydrous dimethyl sulfoxide (DMSO) were purchased from VWR International GmbH (Dresden, Germany). Trifluoroacetic acid (TFA) and acetic acid were purchased from Thermo Fisher Scientific (Schwerte, Germany). Peptide N-glycosidase F (PNGase F) was purchased from N-Zyme Scientifics (Doylestown, PA, USA). Methanol (MeOH) was purchased from Carl Roth GmbH + Co. KG (Karlsruhe, Germany). Milli-Q grade water was produced using a MilliQ Plus water purification system (Merck KGaA, Darmstadt, Germany). All the reagents were obtained in p.a. quality.

The PIM-EA-TB polymer
(Sigma-Aldrich 918784; molecular weight approximately 70 KD; monomer
weight for C₂₁H₂₀N₂ 300 g mol^–1; density approximately 1.1–1.3 g cm^–3 or 3.7–4.3 mmol cm^–3;^{21 (link)} pore volume typically 30–26% (FFV),^{22 (link)} therefore wet density approximately 1.4–1.7 g cm^–3) was synthesized following a previously reported
method.^{23 (link)} Iodomethane (99%), NaClO₄ (≥98.0%), D₂O (99.9% atom D, contains 0.05
wt % 3-(trimethylsilyl)propionic-2,2,3,3-d₄ acid, sodium
salt as the internal standard), dimethyl sulfoxide, DMSO-d₆ (99.9 atom % D), and chloroform were purchased from
Sigma-Aldrich. NaCl (99.5%) was purchased from Fisher Scientific Ltd.
Methanol (HPLC) was purchased from VWR Chemicals BDH. Agarose powder
was purchased from Melford Ltd. All reagents were applied and used
as received without further purification. All aqueous solutions were
prepared with ultrapure water with a resistivity not less than 18.2
MΩ·cm (20 °C), from a CE Instruments water purification
system.