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1.11. DEXTRANS
Dextrans are known in the polysaccharide field mainly because they are
commercially available as standards with narrow molecular weight
distributions over a wide range of molecular weights (< 1000 Da to over 10
6
Da). They are therefore used as standards or calibration substances.
Dextrans are also important on other areas of medicine and biotechnology.
They are known as ‘plasma expanders’ because of their non-ionic and
chemically inert properties. Another area is the development of dextran-based
gel filtration particles, which are chemically cross-linked dextrans of various
porosities and particle sizes (Sephadex).
According to Wikipedia (as of Oct. 2012), ‘.. dextran is synthesized from
sucrose by certain lactic-acid bacteria, the best-known being
Leuconostoc
mesenteroides
and
Streptococcus mutans
. Dental plaque is rich in dextrans.
Dextran is also formed by the lactic acid bacterium
Lactobacillus brevis
to
create the crystals of tibicos, a water kefir fermented beverage which
supposedly has some health benefits. Dextran was first discovered by Louis
Pasteur as a microbial product in wine…’
Dextrans are based on
α
-1,6-linked glucan backbones with different types of
branches:
Haworth formula:
The sugar rings are in the usual
4
C
1
conformation:
O
CH
2
O
OH
OH
OH
O
CH
2
O
OH
OH
OH
O
CH
2
OH
HO
HO
O
O
O
CH
2
OH
HO
HO
O