Tentagel s ram resin

Fmoc-protected amino acids were purchased from CEM Corporation, and Pepceuticals. N, N-Dimethylformamide (DMF) and diethyl ether (Et₂O) were purchased from Rathburn. Triisopropylsilane (TIPS), Trifluoroacetic acid (TFA), N, N-Diisopropylethylamine (DIPEA), N,N’-diisopropylcarbodiimide (DIC), ethyl cyano (hydroxyimino) acetate (Oxyma Pure), fluorescein-5-isothiocyanate (FITC), Fmoc-Lys(Alloc)-OH, Tetrakis(triphenylphosphine)palladium(0) {Pd(PPh₃)₄)}, and phenylsilane were purchased from Fluorochem. Morpholine was purchased from Alfa Aesar. Dichloromethane (DCM) was purchased from VWR. Acetonitrile (MeCN) was purchased from Honeywell. TentaGel S RAM resin was purchased from Rapp Polymere. All other reagents were purchased from Sigma Aldrich.

Proteins, carbohydrates, and other chemicals were purchased from Sigma Aldrich (St. Louis, Missouri, USA) if not stated otherwise. SPPS building blocks and chemicals were purchased from Iris Biotech, GmBH. Nexterion^® Slides H, NHS (SCHOTT, AZ, USA), BI201 human IgG1 was a gift from Bioinvent International AB, Lund, Sweden. D-glucose (Amresco, OH, USA), glyoxylic acid (Merck, Darmstadt, Germany), pyruvic acid (Acros Organics, Geel, Belgium), TentaGel S RAM resin (Rapp Polymere, Tuebingen, Germany), Escherichia. coli XL1-Blue bacteria (Agilent, CA, USA), Ni-NTA agarose (Qiagen, Copenhagen, Denmark), Mini-PROTEAN^®TGX^™ 4–15% Precast gels (BioRad, Copenhagen, Denmark), Micro BCA^™ Protein Assay Kit (Thermo Scientific, MA, USA), OCT/Tissue-Tek (Qiagen, Copenhagen, Denmark), VECTASTAIN ABC HRP Kit (Vector Laboratories, BioNordika, Herlev, Denmark), ImmPACT DAB Peroxidase (HRP) Substrate (Vector Laboratories, BioNordika, Herlev, Denmark), RNAlater^® solution (Qiagen, Copenhagen, Denmark), RNeasy Plus Mini kit (Qiagen, Copenhagen, Denmark), ThermoScript Reverse Transcriptase (Invitrogen, Carlsbad, CA, USA), immunotubes (Thermo Scientific, MA, USA), magnetic streptavidin beads M280 (Invitrogen, Carlsbad, CA, USA), aprotinin (Roche, Basel, Switzerland), SfiI enzyme (New England Biolabs, Ipswich, Massachusetts, USA), Histochoice (Amresco, Solon, OH, USA).

Fmoc-protected amino acids, trifluoroacetic acid (TFA) and N,N-Diisopropylethylamine (DIPEA) were purchased from Combi Blocks (San Diego, CA, USA), Chem-Impex (Wood Dale, IL, USA) or Matrix Innovation (Quebec, QC, Canada). (S)-N-Fmoc-α-(4-pentenyl)alanine and Grubbs 1st Catalyst were obtained from Sigma Aldrich, St. Louis, MO, USA. Palladium (O)tetrakis(triphenyphosphine) (Pd(PPh₃)₄) was purchased from Strem Chemicals, Newburyport, MA, USA. TentaGel™ S RAM resin was purchased from Rapp Polymere, Tübingen, Germany. N,N-Dimethylformamide (DMF) and diethyl ether (Et₂O) were purchased from Fischer Scientific, Hampton, NH, USA. All other reagents were purchased from Sigma Aldrich.
SARS-CoV-2 (2019-nCoV) Rabbit Mab neutralizing antibody was obtained from Sino Biological, Beijing, China (Catalog No. 40592-R001, HA140C2601). All media and supplements for cell maintenance were obtained from Life Technologies Ltd. (Paisley, UK), except otherwise stated.

Three peptide libraries [KGDE]-[DE]-[ST]-[DE]₃-NH₂, [KGDE]-[DE]-[S]-[DE]₄-NH₂ and [KGDE]-[DE]-[T]-[DE]₄-NH₂ were synthesized by standard solid-phase peptide synthesis on TentaGel S RAM resin (Rapp polymere) using a Prelude peptide synthesizer (Protein technologies) with equimolar peptide building blocks. Side chain protecting groups were Boc, tBu and OtBu for Lys, Ser/Thr and Asp/Glu respectively. Cleavage was performed with 95:2.5:2.5% trifluoroacetic acid (TFA):triisopropylsilane:H₂O, and the resulting peptides were precipitated with cold diethyl ether, centrifuged, the pellets were then dissolved in H₂O and finally lyophilized. The compositions of libraries were analyzed by ESI-MS⁴¹ . To avoid losing single peptides, the products were purified by dialysis against TBS buffer (25 mM Tris-HCl, 0.15 M NaCl, pH 7) and verified by ESI-MS using LC-MS separation on RP-C18 resin.