Conformational analysis of segments of oxidized cellulose. Part I: Molecular modelling of glucuronic acid dimers considering the effect of counter-ions and a polar environment.
Conformational analysis of various forms of glucuronic acid dimers as the model structures of oxidized cellulose has been performed using molecular mechanics with a CVFF force field. The effects of ionization of carboxyl groups, ion pairing with explicit consideration of counter-ions (Na+, Mg2+) and the implicit inclusion of a solvent effect via the dielectric constant, epsilon, have been simulated. The non-ionized glucuronic acid dimer shows conformational behaviour similar to that of unoxidized cellobiose. The ionization of COOH groups leads to strong destabilization of C and D conformers (with both COO- groups on the same side of the molecule), while complexation with counter-ions leads to strong stabilization of these forms which yield highly wound low-pitch helices. An increase in the solvent polarity has an attenuating effect on the behaviour described above.
Miertus
S
S
POLY-biòs, Trieste, Italy.
Bertocchi
C
C
Krempaska
R
R
Paoletti
S
S
D000838:Anions; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002475:Cellobiose / Q000737:chemistry*; D002482:Cellulose / Q000737:chemistry*; D004187:Disaccharides / Q000737:chemistry*; D005965:Glucuronates; D020723:Glucuronic Acid; D008274:Magnesium; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D012964:Sodium; D012984:Software; D012997:Solvents
D000838:Anions; D004187:Disaccharides; D005965:Glucuronates; D012997:Solvents; D002475:Cellobiose; D020723:Glucuronic Acid; D002482:Cellulose; D012964:Sodium; D008274:Magnesium