Ionic polysaccharides. V. Conformational studies of hyaluronic acid, cellulose, and laminaran

Autor: Robert L. Cleland
Rok vydání: 1971
Předmět:
Zdroj: Biopolymers. 10:1925-1948
ISSN: 1097-0282
0006-3525
DOI: 10.1002/bip.360101012
Popis: Hindered rotation was studied for the disaccharides composed of basic β-glucopyranose units A (linked at O1 and O4) and B (linked at O1 and O2) in Cl conformation. The van der Waals' interactions were calculated for the Lennard-.Jones, Buckingham, and Kitay-gorodsky interatomic potential functions, including a study of the effect of minimization of the first two functions for each atomic pair k, m (a) at the sum rkm* of the usual crystal atomic radii rk* + rm* and (b) at rkm* + 0.2 A. Values of the ratio of unperturbed to free-rotation root-mean-square end-to-end distance σ, were calculated for chains composed of the unsolvated disaccharide repeating units: AA (cellulose), AB and BA (hyaluronic acid), and BB (laminaran). For cellulose and hyaluronic acid, σ increases markedly with both assumed atomic radii rk* and θ, the supplement of theglycosidebond angle. Energy contributions from dipole–dipole and side-chain interactions cause relatively small dimensional changes for hyaluronic acid: for cellulosic polymers bulky side groups attached near the glycoside carbon atom may increase or decrease unperturbed dimensions, depending on the potential function chosen. Inclusion of bond torsional potentials increases σ for cellulose and hyaluronic acid and decreases σ for laminaran. Hydrogen-bonding ellects normally increase calculated σ values for unsolvaled polymers. The predicted influence of temperature on σ is small. The large decrease in σ with increasing temperature which appear to occur experimentally for cellulosic polymers are prc.-umably due to conformational effects of solvation.
Databáze: OpenAIRE
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