Hplc supra gradient acetonitrile

Disodium hydrogen phosphate dihydrate, potassium dihydrogen phosphate, sodium chloride and trifluoroacetic acid were obtained from Merck (Darmstadt, Germany). From Sigma-Aldrich (Steinheim, Germany) ammonium bicarbonate, formic acid, potassium chloride and tolylsulfonyl phenylalanyl chloromethyl ketone-treated trypsin from bovine pancreas were purchased. The Visucon-F pooled healthy human plasma standard was obtained from Affinity Biologicals (Ancaster, Canada). HPLC-supra-gradient acetonitrile originated from Biosolve (Valkenswaard, The Netherlands). From GE Healthcare (Uppsala, Sweden) protein G Sepharose 4 Fast Flow beads were purchased. Recombinant trimerized S protein was prepared as described previously (31 (link)). An ELGA Purelab Ultra system (Elga LabWater, High Wycombe, United Kingdom) was used to produce type I Ultrapure Water that was used in solutions throughout.

Type I Ultrapure Water was produced by an ELGA Purelab Ultra system (Elga LabWater, High Wycombe, United Kingdom) and used to create solutions throughout. Ammonium bicarbonate, potassium chloride, formic acid, tolylsulfonyl phenylalanyl chloromethyl ketone-treated trypsin from bovine pancreas was obtained from Sigma-Aldrich (Steinheim, Germany). Trifluoroacetic acid, disodium hydrogen phosphate dihydrate, potassium dihydrogen phosphate, and sodium chloride were purchased from Merck (Darmstadt, Germany). HPLC-supra-gradient acetonitrile was obtained from Biosolve (Valkenswaard, The Netherlands). The Visucon-F pooled healthy human plasma standard originated from Affinity Biologicals (Ancaster, Canada). Protein G Sepharose 4 Fast Flow beads were obtained from GE Healthcare (Uppsala, Sweden). Recombinant trimerized S protein was prepared as described.¹⁵ (link)

For preparation of FDOPA the 6-trimethylstannyl-L-DOPA precursor was purchased from ABX (Germany). Dry chloroform >99 % for spectroscopy stabilized with amylene (stored on molecular sieves) and ammonium dihydrogen phosphate p.a. were obtained from Acros (Belgium) and 47 % hydrobromic acid, 25 % ammonia and diammonium hydrogenphosphate p.a. from Merck (Germany). A sterile solution for injection of ascorbic acid (100 mg/ml) was purchased from Centrapharm (Netherlands). A sterile 0.1 M sodium acetate solution, pH 4.7, was prepared in the hospital pharmacy. Reference compounds for calibration curves of FDOPA, L-DOPA and 6-hydroxy-DL-DOPA were purchased from respectively ABX (Germany) and Sigma Aldrich (Netherlands), HPLC supra gradient acetonitrile, used as solvent for LC-MS analysis, was obtained from Biosolve (Netherlands), ~98 % formic acid was bought from Fluka (Netherlands) and LC-MS grade water (>18.2 MΩ) was purchased from the Department of Clinical pharmacy & Pharmacology, UMCG. The reference compound leucine encephalin for calibration of the MS detector was purchased from Merck (Germany). For calibration of the MS, a solution was prepared of 200 μL 10 % formic acid, 100 μL 0.1 M sodium hydroxide (Merck, Germany) and 20 ml 80 % acetonitrile in water.