Amino acids

All reagents and solvents were purchased from commercial sources. Amino acids and 2-chlorotrityl-chloride (CTC) resin were obtained from (Iris Biotech, Marktredwitz, Germany) and N,N-Diisopropylethylamine (DIEA) from (Sigma-Aldrich, St. Louis, MO, USA). N,N,N′,N′-tetramethyl-O-(1H-benzotriazol-1-yl)uronium hexafluorophosphate (HBTU) and 1-cyano-2-ethoxy-2-oxoethyliden(aminooxy) dimethylamino-morpholino-carbenium hexafluoro phosphate (COMU) were a gift from Luxembourg Technologies. Organic solvents were supplied by (Merck, Darmstadt, Germany).

Unless otherwise specified, reagents were obtained from commercial sources. LC-MS grade water was purchased from Huberlab (Aesch, Switzerland); methanol and acetonitrile (both HPLC gradient grade) were purchased from VWR (Darmstadt, Germany). Ammonium formate and formic acid were purchased from Sigma-Aldrich (Buchs, Switzerland). Other solvents and reagents were purchased from Merck (Darmstadt, Germany). Fmoc-Arg(Pbf) Wang resin was obtained from Activotec (Cambridge, UK). Amino acids and coupling reagents were purchased from Iris Biotech (Marktredwitz, Germany). Recombinant human receptors and biotinylated human VEGF-A₁₆₅ were purchased from R&D Systems (Minneapolis, MN, USA). Chemiluminescent, streptavidin-horseradish peroxidase conjugate and DPBS were obtained from Thermo Scientific (Waltham, MA, USA).

Resin, amino acids and activators were purchased from Iris Biotech GmbH (Marktredwitz, Germany). N-ethyldiisopropylamine (DIPEA) and bromophenol blue (BPB) were purchased from Merck KGaA (Darmstadt, Germany).
All the abbreviations used can be found in Abbreviation.