Human Sn(d1-4)Fc binds preferentially to PAA glycoconjugates carrying 3′-sialyllactose.

Fc proteins were coated onto plastic microwells, and biotinylated PAA glycoconjugates linked either to 3′-sialyllactose (2,3-PAA, panel A) or 6′-sialyllactose (2,6-PAA, panel B) were added at the indicated concentrations. Unbound conjugate was washed off and binding detected with streptavidin-peroxidase and o-phenylenediamine dihydrochloride as substrate. ● indicates hSn(d1-4)Fc, and comparisons were made with CD22-Fc (▾) that binds specifically to 2,6-PAA and NCAM-Fc (○), a control protein that does not mediate sialic acid binding. Data show mean absorbance values ± range of duplicates and are representative of 2 experiments performed.