Fig. 1: Glycan library screening and glycan affinities for RBD and S protein.
From: Sialic acid-containing glycolipids mediate binding and viral entry of SARS-CoV-2
a,b, Normalized abundances of released glycans from the SARS-CoV-2 RBD and S protein by CaR-ESI-MS at 37 °C. Summary of the charge-normalized (relative to 69) abundances (Abrel) of released ligands (L) measured by CaR-ESI-MS screening of libraries A–O against SARS-CoV-2 RBD (a) and S protein (b). Measurements were performed in negative ion mode with an ultrahigh mass range (UHMR) Orbitrap mass spectrometer on aqueous ammonium acetate (100 mM, pH 6.9) solutions of RBD (10 μM) and glycan library (A–O) and library P (50 nM of each glycan) or S protein (280 μg ml–1) and glycan library (A–O) and library P (500 nM of each glycan). A high-energy C-trap dissociation (HCD) energy of 50 V (using nitrogen as collision gas) with an isolation window of m/z 3,000–4,000 was used for screening against RBD; an HCD energy of 300 V (using argon) with an isolation window of m/z 8,000–15,000 was used for screening against S protein. The different classes of oligosaccharides are distinguished by color: red, Lewis antigens (1–14); yellow, blood group A antigens (15–20); orange, blood group B antigens (21–26); green, blood group H antigens (27–32); blue, sulfated compounds (34–38) and HS oligosaccharides (39–41); light blue, antigen-related glycans (42–50); purple, globo (51–60); pink, ganglioside oligosaccharides (61–76); white, HMOs and other glycans (77–128); light gray, Neu5Acα2-6-linked oligosaccharides (129–132); dark gray, rhamnose-containing compounds (133–139); NA, not applicable. An asterisk indicates that the relative abundances (in CaR-ESI-MS) were estimated from their relative (to 69) Kd. Data represent mean ± s.d.; n = 3 independent experiments. c, Affinities of glycans (15, 21, 27, 35, 36, 39–41, 69, 71, 76, 129 and 140) for RBD. Kd (μM) values were measured by ESI-MS using aqueous ammonium acetate (100 mM, pH 6.9) solutions containing RBD (5 μM) and each glycan (three different concentrations ranging from 30 to 150 μM) at 25 °C (white bars) and 37 °C (black bars); ND, not detected. Data represent mean ± s.d.; n = 3 independent experiments for each glycan concentration.
