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Structure and conformation of acetan polysaccharide
C Ojinnaka1, A J Jay, I J Colquhoun
1Department of Food Science and Technology, Cranfield University, Silsoe College, Bedford, UK.
International Journal of Biological Macromolecules
|October 1, 1996
Summary
Acetan, an anionic bacterial polysaccharide, features acetylation on specific glucose residues. Despite acetylation, acetan exhibits a thermoreversible helix-coil transition in solution, indicating structural flexibility.
Area of Science:
- Carbohydrate Chemistry
- Biochemistry
- Structural Biology
Background:
- Acetan is an anionic bacterial polysaccharide with a complex repeat unit.
- Its structure involves a cellobiose core and a charged pentasaccharide sidechain.
- The repeat unit contains two acetylation sites.
Purpose of the Study:
- To elucidate the precise locations of acetylation on the acetan polysaccharide.
- To investigate the conformational behavior of acetan in aqueous solution.
- To determine the impact of acetylation on acetan's structural transitions.
Main Methods:
- Nuclear Magnetic Resonance (NMR) spectroscopy (1H and 13C).
- Methylation studies (basic and mild).
- Optical rotation, circular dichroism, and Differential Scanning Calorimetry (DSC).
Main Results:
- Acetylation was confirmed at C6 on the (1,2)D-Man and (1,34)D-Glc residues.
- Evidence for a thermoreversible order (helix)-disorder (coil) transition was observed.
- The studies suggest acetylation does not impede helix formation.
Conclusions:
- The specific acetylation sites on acetan were identified.
- Acetan undergoes a reversible conformational transition in solution.
- Acetylation of the polysaccharide backbone does not prevent helix formation.