Biomedical Engineering Reference
In-Depth Information
B
1
C
1
B
2
C
2
3,5
A
3
CH
2
OH
CH
2
OH
CH
2
OH
O
O
O
O
RO
O
OR
1
1,5
X
0
HO
OH
HO
OH
NHAc
HO
Y
1
Y
2
CH
2
OH
CH
2
OH
CH
2
OH
O
O
O
RO
RO
RO
OH
HO
HO
OH
OH
HO
C ion
B ion
E ion
CH
2
OH
CH
2
OH
CH
2
OH
O
O
RO
O
RO
OH
HO
OH
OH
D ion
3,5
A ion
CH
2
OH
CH
2
OH
O
O
O
O
OR
1
HO
OR
1
NHAc
HO
HO
NHAc
Y ion
1,5
X ion
Fig. 8.2. Domon and Costello nomenclature for describing the fragmentation of carbo-
the elimination of the lower antenna that is linked to the
3-position of core
β
-mannose. For example, the D
2
ion (at
m/z
347 Da) in
Fig.
8.3a
is 180 mass unit less than its corre-
sponding C
2
ion because it has lost mannose (162 Da) and
H
2
O (18 Da) due to the elimination process. The struc-
ture shown in
Fig.
8.3b
has no lower antenna and so loses
water (18 Da) only from the C
2
fragment to give the D
2
ion
at
m/z
347. These characteristic D ions are therefore par-
ticularly useful for determining antenna positions and their
substitutions.
3. Another abundant ion occurs by fragmentation of the glyco-
sidic linkage between the two
N
-acetylglucosamine residues
in the chitobiose core to give a B
n
ion. Its corresponding
C ion is normally minor by comparison (
see
B
3
and C
3
in
4. These B
n
ions are often accompanied by E
n
ions, which
occur by elimination of the substituent from the C-2 posi-
tion.
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