Structure of GAS 914 and inhibition of αGal IgG, IgM, and HAPAb. (a) Chemical structure of random copolymer with: n, average degree of polymerization; x, fraction of glycosylated monomer; 1 – x, fraction of thioglycerol-capped monomer. Arrows indicate the positions labeled with ¹⁴C for pharmacokinetic studies. (b) Atomic force microscopy of GAS914 shows a chain-like molecule with an average chain diameter of 4.0 ± 0.2 nm and average chain length of 79 ± 24 nm. (c) Inhibition curves of αGal IgG (IC₅₀ monomer = 54 μM, IC₅₀ GAS914 = 0.028 μM). (d) Inhibition curves of αGal IgG (IC₅₀ monomer = 332 μM, IC₅₀ GAS914 = 0.043 μM. (e) Inhibition curves of HAPAb (IC₅₀ monomer = 400 μM, IC₅₀ GAS914 = 0.004 μM. Concentrations shown are on a per oligosaccharide basis as indicated in Methods. Curves are representative of more than seven experiments performed on different days.