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273
Xanthan
8
O
CH
2
OH
OH
OH
O
CH
2
OH
OH
O
CH
2
O
Ac
OH OH
O
COO
-
Na
+
OH
OH
O
CH
2
OH
OH
O
O
O
O
O
O
O
+
Na
-
OOC
H
3
C
n
β
-Man
GlcA
α
-Man
Acetate:
H
3
C
O
O
Pyruvate
diketal
• Bacterial polysaccharide (extracellular).
•
Xanthomonas campestris
(plant pathogen)
• Pentasaccharide repeating units:
Backbone as cellulose
(β-1,4-linked D-glucose)
• O-acetylated at O-6 of the α-Man
• Pyruvate diketal at the terminal β-Man
9
200 nm = ca 200 repeating units
Xanthan: A large and expanded polysaccharide
Splitting of double-strand