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Molecular origins of acetan solution properties
V J Morris1, G J Brownsey, P Cairns
1AFRC Institute of Food Research, Norwich Laboratory, UK.
International Journal of Biological Macromolecules
|December 1, 1989
Summary
Acetan, a heteropolysaccharide from Acetobacter xylinum, forms non-crystalline helices. Its helical structure is retained in solution but transitions upon heating, exhibiting high viscosity and shear-thinning behavior.
Area of Science:
- Biochemistry
- Polymer Science
- Microbiology
Background:
- Acetan is a branched acidic heteropolysaccharide.
- It is secreted by the bacterium Acetobacter xylinum.
Purpose of the Study:
- To investigate the structural properties of acetan.
- To understand the behavior of acetan in aqueous solutions.
Main Methods:
- X-ray diffraction studies on oriented fibers.
- Optical rotation measurements.
- Circular dichroism spectroscopy.
- Rheological measurements (viscosity).
Main Results:
- X-ray diffraction indicated non-crystalline helices with fivefold symmetry and a 4.8 nm pitch.
- Optical rotation and circular dichroism confirmed helical structure in solution.
- A helix-coil transition was observed upon heating and cooling.
- Aqueous solutions displayed high low shear rate viscosity and shear-thinning properties.
Conclusions:
- Acetan possesses a stable helical conformation in solution.
- Thermal transitions (helix-coil) influence acetan's structure.
- Acetan's rheological properties are characteristic of a polymer exhibiting chain entanglement and shear-dependent flow.