Supplemental Figure S1. MALDI-TOF/TOF MS analysis of mouse serum glycans. MS/MS spectra were annotated using GlycoWorkbench

software which calculates the percentage of experimental fragments that match with the theoretical fragments generated in silico. For each m/z

value, the shown structure is the one which presented the largest number of fragments that match with the theoretical fragments. Only the B-, C-, Y-

and Z-type ions are shown. The B- and C-type ions resulting from terminal reductive fragmentation are not systematically illustrated by the

software. Most of the observed ions were sodiated. However, the sodiated ion with m/z 428 (NeuGc) has given rise to the ion with m/z 406, which is

a desodiated and protonated form of the ion with m/z 428, and to the ion with m/z 374, which is a decarboxylated form of the ion with m/z 406. The

ions with m/z 374 and 406 were frequently observed on the MS/MS spectra.

Supplemental Figure S1

1580Parent ion with m/z

1784

* The methodology for the extraction of N-glycans can introduce free O-glycans from serum. Therefore, ions 428, 877 and 953 likely are fragments of the parent ion 1807 that

matches with a O-glycan ( ).

Ions 472 and 1389 are fragments of the parent ion 1795.

Parent ion with m/z

*877

472

*428

1389

*953

1795

*1807

1795

* Ions 428 and 877 are fragments of the parent ion 1807.

Ions 1506 and 1565 are fragments of the parent ion 1784.

Parent ion with m/z

*8771506

1565

1784

*1807

*428

1836

* Ions 877 and 953 are fragments of the parent ion 1807 wich is likely a O-Glycan (see parent ion 1784).

Remark: more fragments match with a structure showing a fucose on the terminal GlcNAc rather than a structure with a fucose on the reductive terminal GlcNAc.

Parent ion with m/z

*877 *1807*953

1988

* Ions 374, 406, 472, 877, 1606 and 1795 are fragments of the parent ion 2012.

Ions 1576 and 1593 are fragments of the parent ion 1999.

Parent ion with m/z

1999

*2012

*1795

*1606

1593

1576

*877

*472*406

*374

1999

* Ions 877 and 1606 are fragments of the parent ion 2012

Parent ion with m/z

*877

*1606

*2012

2012

* Ion 1592 is a fragment of ion 1999.

Parent ion with m/z

*1999

*1592

2040

*428

*877

*1157

*2012

* Ions 428, 877 and 1157 are fragments of the parent ion 2012

Parent ion with m/z

2192

* 374, 406, 428, 472, 877, 1780 and 1998 are fragments of the parent ion 2186, a monoantennary fucosylated and sialylated (NeuGc) glycan.

Parent ion with m/z

*2186

*374

*406

*428

*472

*877

*1780

*1998

2216

* 1317, 1781 and 1837 are fragments of the parent ion 2244.

Parent ion with m/z

*2244*1837

*1781

*1317406

374

2244

* 374, 406, 650, 877, 1852, 1980 and 1999 are fragments of the parent ion 2257.

1361 can be attributed to the protonated Z-type ion that comes from ion 2257 (see parent ion with m/z 2257).

Parent ion with m/z

*406*374

*877

*650

*1852

*1980

*1999

*2257

1361

2257

*2244

1361

*1837

406

374

* Ion 1837 is a fragment of the parent ion 2244.

Ion 1361 can be attributed to the protonated Z-type ion:

Parent ion with m/z

2396

*877

*472*428

*406

*374

1268

*2420

*1565

*1592

*2144

*1984

*1995

*2014

* Ions 374, 406, 428, 472, 877, 1565,1592, 1984, 1995, 2014,2144 are fragments of the parent ion 2420.

Ion 1268 was not able to be attributed.

Parent ion with m/z

2420

*2448

*2042

* Ion 2042 is a fragment of the parent ion 2448.

BY

CZ

406

374

Parent ion with m/z

2448

*2461

*877*650

* Ions 650 and 877 can be attributed to ion 2461.

Remark: more fragments matched with a structure displaying a fucose on antennae with Gal-Gal motif.

Parent ion with m/z

2461

406

374

*2448

*2042

* Ion 2042 is a fragment of the parent ion 2448.

Parent ion with m/z

2607

*2635

*2230

*2173

*374

*406

*472

*877

855

*1081*1317

* Ions 374, 406, 472, 855, 877, 1081, 1317, 2173 and 2230 are fragments of the parent ion 2635.

Ion 855 is a protonated and desodiated form of the ion 877.

Remark: More ions match with a structure showing a substituted LacNAc antennae instead of a polysialylated structure.

Parent ion with m/z

2635

*406

*374

196

*855

1752

1998

* Ions 374, 406 and 855 are fragments of the parent ion 2635.

Ions 196, 1752 and 1998 were not able to be attributed to a parent ion.

Parent ion with m/z

*2809

*877

*650*1720

*1983 *2433

*406

*374

1143

1593

2448

2822§ 819

*855*428

§ 196

2796

* Ions 374, 406, 650, 855, 877, 1720, 1983 and 2433 are fragments of the parent ion 2809.

Ions 1143, 1593, 1998 and 2448 are fragments of the parent ion 2822.

§ Ions196 and 819 were not able to be attributed to a parent ion.

1998

Parent ion with m/z

2809

406

374 *939

*1143

*1592 *1793

*1998

*2244

*2448

*2822

* Ions 939, 1143, 1592, 1793, 2244 and 2448 are fragments of the parent ion 2822.

Ions 374 and 406 are fragments of the parent ion 2809.

Parent ion with m/z

2822

2837

2852

Parent ion with m/z

2837

* Ions 428, 877, 1081, 1143, 1592, 1793, 1998, 2242, 2447 and 2576 are fragments of the parent ion 2852.

*428

*877

*1081*1143 *1592

*1793

*1998

*2242

*2447

*2576

*2852

Parent ion with m/z

2852Parent ion with m/z

2867

*877

*1143

*2852

*1997

*2447

* Ions 877, 1143, 1997 and 2447 are fragments of the parent ion 2852.

Parent ion with m/z

2895

*877

*939

*2056

*2448

*2505

*2910

2852

* Ions 877, 939, 2056, 2448 and 2505 are fragments of the parent ion 2910.

Parent ion with m/z

2910Parent ion with m/z

3026

406

374

Parent ion with m/z

3056

*3026

*2622

*2173

406

374

* Ions 1967, 2173 and 2622 are fragments of the parent ion 3026.

Ion 855 is a protonated and desodiated form of ion 877.

855 *1967

Parent ion with m/z

3228

*3244

*2839

*1998

*1268*877

*650*406

*374

* Ions 374, 406, 650, 877, 1268, 1998 and 2839 are fragments of the parent ion 3244.

Parent ion with m/z

3244Parent ion with m/z

3259

*3244

*2839

*1997

*1793

*1268

406

374

* Ions 1268, 1793, 1997 and 2839 are fragments of the parent ion 3244.

Ions 374 and 406 are fragments of the parent ion 3259.

Parent ion with m/z

3288

*3244

*2839

*1997

*1268

406

374

* Ions 1268, 1997 and 2839 are fragments of the parent ion 3244.

Ions 374 and 406 are fragments of the parent ion 3288.

Parent ion with m/z

3302

*3244

*2839

*1997*1268

* Ions 1268, 1997 and 2839 are fragments of the parent ion 3244.

Parent ion with m/z

3635Parent ion with m/z

*3663

*2839

*877

*650

*428

*406

*374

* Ions 374, 406, 428, 650, 877 and 2839 are fragments of the parent ion 3663.

3663

1

2

* 2839

* 3288

406

374

Two potential structures (1 and 2) were observed, but more fragments matched with the structure 1 than the structure 2.

* Ions 2839 and 3288 are fragments of the parent ion n°2.

Ions 374 and 406 are related to NeuGc sialic acid

Parent ion with m/z

3678

*3693

*3288

*2839

*1983*1268

406

* Ions 1268, 1983, 2839 and 3288 are fragments of the parent ion 3693.

Ion 406 is related to NeuGc sialic acid.

Parent ion with m/z

3693Parent ion with m/z

406

3708

406

374 *1268 *1984

*2433

*3288

*3693

* Ions 1268, 1984, 2433 and 3288 are fragments of the parent ion 3693.

Parent ion with m/z

*406

*374 *650 *877

*2837

*3230

*4128

4084Parent ion with m/z

* Ions 374, 406, 650, 877, 2837, 3230 are fragments of

the parent ion 4128 ( )