Sugars residue masses

Fig. 11.—Sequence of a 2S-Sugar Residue Glycosphingolipid Isolated from Rabbit Erythrocyte Membranes. (Cleavage points, and the masses of fragment ions of the permethylated derivative, are shown. No fragment-ions were observed above 4000, because of the poor sensitivity at high mass.)...

The methyl-substitution pattern of the neutral sugar residues can be reliably identified from their mass spectra.41-43 Identification of the substitution pattern from the electron-impact, mass spectra rarely presents any major problems. It should, however, be noted that, in some cases, the occurrence of symmetrical molecules jeopardizes the identification. An example of this is the symmetrical, 3,4-di-O-methyl derivative (6) of mannose, which is commonly found in the analysis of... 

Table 20.1 Residue masses of some monomeric sugar units ...

The molecular mass of a oligosaccharide can be calculated from residue masses of individual sugar units in the molecule from M = 18 + S (Residue masses of monomeric units). Residue masses of some important monomeric units are given in Table 20.1. Relevant sugar monomer stmctures are shown in Figure 20.1. 

---