Table 1.
Reaction Efficiency of Sialic Acid by p-Toluidine Carbodiimide Coupling in the Presence of EDC at pH 4–6a
| Glycan | Glycan abundance after sialic acid modification by Carbodiimide coupling (normalized by DP7) (%)
|
Remarks | |||||
|---|---|---|---|---|---|---|---|
| 0 min | 10 min | 30 min | 60 min | 120 min | 240 min | ||
1663.2
|
46.5 ± 6.5 | 25.5 ± 2.5 | 13.5 ± 6.3 | 8.0 ± 3.0 | 7.5 ± 3.2 | 4.1 ± 0.9 | Loss two sialic acids |
1977.3
|
27.3 ± 3.1 | 17.02 ± 1.6 | 5.8 ± 1.5 | 2.2 ± 0.4 | 1.1 ± 0.5 | 0.24 ± 0.1 | Loss one sialic acid, without modification |
2290.2
|
25.58 ± 1.38 | 14.9 ± 4.0 | 4.6 ± 0.8 | 1.9 ± 0.3 | 1.1 ± 0.3 | 0.71 ± 0.3 | Two sialic acids, without modification |
2357.2
|
0.40 ± 0.01 | 27.7 ± 4.4 | 27.7 ± 2.9 | 18.0 ± 2.9 | 14.8 ± 1.9 | 1.78 ± 0.3 | Two sialic acids, one of them modified by p-toluidine |
2424.3
|
0.27 ± 0.09 | 14.8 ± 3.8 | 49.3 ± 4.6 | 69.8 ± 9.7 | 75.4 ± 5.9 | 93.2 ± 3.4 | Both sialic acids modified by p-toluidine |
a
100 μg of SGP is immobilized to 100 μL of Aminolink beads for carbodiimide coupling. An internal standard DP7 (1 μL, 1μM in DI) is spiked to normalize the intensity. blue ■: N-acetylglucosamine; green ●: mannose; yellow ●: galactose; pink ◆: N-acetylneuraminic acid; pink and gray ⬣: p-toluidine.