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1,000 10,000 100,000 1,000,00010,000,000
M
w
1
10
100
1,000
10,000
Intrinsic viscosity (ml/g)
I = 0.1 M
Xanthan
(double stranded)
Alginate
(mannuronan)
Lignosulfonate
1.7. XANTHAN: FUNDAMENTALS
(KEYWORDS)
•
Bacterial polysaccharide (extracellular).
Xanthomonas campestris
(plant pathogen)
•
Pentasaccharide repeating units:
•
O-acetylated at O-6 of the α-Man
•
Pyruvate diketal at the terminal β-Man
•
Water soluble
•
Double-stranded, stiff structure.
•
Retains viscosity at high ionic strength (no collapse)
•
May dissociate into more flexible single strands at high T (depends on I
(ionic strength))
•
Very high M
w
(typically > 10
6
g/mol)
•
q (persistence length) = ca. 120 nm. One of the stiffest polysaccharide
structures known.
•
Important industrial polysaccharide (E415): Viscosifyer, stabilizer
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
200 nm