Peak no. in Figure. 2 Time (min) Site Fragment Amino acid sequencea Carbohydrate Charge state Observed m/z Measured　mass Monoisotopic mass 1 3.3 64 60-65 AATVND [Fuc][GlcNAc]2[Man]3 2+ 814.79 1627.58 1627.65 2 3.7 64 60-68 AATVNDSGE [Fuc][GlcNAc]2[Man]3 2+ 951.35 1900.69 1900.74 3 5.4 162 157-166 LVGSKNVSSE [Fuc][GlcNAc]2[Man]3 2+ 1029.43 2056.86 2056.91 4 10.8 - 149-156 SGSYFCRG - 2+ 467.68 933.34 933.37 5 12.3 38, 45 37-46 DNSTQWFHNE [Fuc][GlcNAc]2[Man]3 [GlcNAc]2[Man]3 [Fuc][GlcNAc]2[Man]3 [Fuc][GlcNAc]2[Man]3 3+ 3+ 1070.02 1118.74 3207.06 3353.22 3207.20 3353.26 6 13.3 38, 45 37-46 DNSTQWFHNE [GlcNAc] [Fuc][GlcNAc]2[Man]3 2+ 1259.93 2517.86 2517.97 7 14.9 169 167-175 TVNITITQG [Fuc][GlcNAc]2[Man]3 2+ 992.92 1983.84 1983.89 8 16.0 162 149-166 SGSYFCRGLVGSKNVSSE [Fuc][GlcNAc]2[Man]3 3+ 991.72 2972.16 2972.30 9 22.2 74 69-85 YRCQTNLSTLSDPVQLE [Fuc][GlcNAc]2[Man]3 3+ 1021.75 3062.25 3062.33 aC: Carboxymethyl cysteine

Table 1: MS data for glycopeptides in the Glu-C digest of sFcγRIIIb.