Table 2. Characterization of conjugates by MALDI-MS.

Conjugate	MW of receptor	MW of MSA	Average MW of conjugate	Receptor/MSA
A (avian receptor) α-2,3-sialyllactoside-MSA	770	65,859	79,646	18
B (human receptor) α-2,6-sialyllactoside-MSA	770	65,859	77,332	15

The ratio of receptors to MSA was estimated by mass spectrometry analysis. MSA has a molecular weight of 65,859 Dalton by MALDI-MS, whereas the molecular weights of the α-2,3- and α-2,6-sialyllactoside conjugates are averaged around 79,646 Da and 77,332 Da, respectively, indicating 18 molecules of α-2,3-sialyllactoside are attached to MSA, and 15 of α-2,6-sialyllactoside to MSA.