Ordered conformation of xanthan in solutions and "weak gels": single helix, double helix – or both?

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Morris, Edwin R.
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Elsevier Ltd
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During the progress of xanthan from a recent discovery to its present status as a well-established food hydrocolloid, some investigations have indicated that the ordered structure, which underlies most of the practical applications of xanthan, is a single helix stabilised by ordered packing of sidechains along the polymer backbone, giving first-order kinetics for the disorderâ order transition. Others favoured a coaxial double helix, whose formation causes a doubling of molecular weight and mass per unit length. It is proposed here that both interpretations are correct, and that ordering is a 2-stage process: formation of single helices followed, under favourable conditions, by enthalpically-driven conversion to coaxial double helices. Comparison of recent evidence from atomic force microscopy with models from analysis of X-ray fibre diffraction data suggests that the most likely coaxial arrangement is an antiparallel 51 double helix.
Xanthan , Conformation , Single helix , Double helix , Light scattering , Optical rotation
Morris, E. R. (2017) 'Ordered conformation of xanthan in solutions and "weak gels": single helix, double helix – or both?', Food Hydrocolloids, 86, pp. 18-25. doi:10.1016/j.foodhyd.2017.11.036