Glycobiology Advance Access originally published online on December 17, 2002
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Glycobiology, 2003, Vol. 13, No. 4 255-264
© 2003 Oxford University Press
Predicting the molecular shape of polysaccharides from dynamic interactions with water
2 Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU United Kingdom
3 Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
Received on July 29, 2002; revised on October 30, 2002; accepted on November 21, 2002
How simple monosaccharides, once polymerized, become the basis for structural materials remains a mystery. A framework is developed to investigate the role of water in the emergence of dynamic structure in polysaccharides, using the important ß(1
4) linkage as an example. This linkage is studied within decasaccharide fragments of cellulose, chitin, mannan, xylan, and hyaluronan, using molecular simulations in the presence of explicit water solvent. Although cellulose, mannan, chitin, and xylan are chemically similar, their intramolecular hydrogen-bond dynamics and interaction with water are predicted to differ. Cellulose, mannan, and chitin favor relatively static intramolecular hydrogen bonds, xylan prefers dynamic water bridges, and multiple water configurations are predicted at the ß(14) linkages of hyaluronan. With such a variety of predicted dynamics, the hypothesis that the ß(14) linkage is stabilized by intramolecular hydrogen bonds was rejected. Instead, it is proposed that favored molecular configurations are consistent with maximum rotamer and water degrees of freedom, explaining observations made previously by X-ray diffraction. Furthermore, polysaccharides predicted to be conformationally restricted in simulations (cellulose, chitin, and mannan) prefer the solid state in reality, even as oligosaccharides. Those predicted to be more flexible (xylan and hyaluronan) are known to be soluble, even as high polymers. Therefore an intriguing correlation between chemical composition, water organization, polymer properties, and biological function is proposed.
1 To whom correspondence should be addressed; e-mail: andrew.almond{at}bioch.ox.ac.uk
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