Atomistic Insights into Conformations and Solvation Dynamics of Amylose, Dextran, and Pullulan Using Three Force Fields.

Molecular dynamics (MD) simulations of three α-glucans─amylose, dextran, and pullulan─were performed in explicit solvent to investigate how differences in their glycosidic linkages influence molecular conformation and solvation dynamics, and to assess the performance of three major force fields (FFs): CHARMM36, GLYCAM06, and OPLS-AA. Structural analysis revealed that amylose adopts a more extended and constrained conformation owing to its α-(1 → 4) linkages, whereas dextran and pullulan exhibit more collapsed structures. Differences in linkage chemistry also influenced the organization of surrounding water, with this effect more pronounced in CHARMM than in GLYCAM or OPLS. Dextran formed more stable hydrogen bonds with water than amylose or pullulan. Although glucan-water nonbonded interactions were energetically more favorable in GLYCAM and OPLS, these FFs also predicted stronger nonpolar interactions that promoted more compact glucan conformations. Overall, the results indicate that glucan-glucan interactions contribute comparably to glucan-water interactions in determining polysaccharide structure. These insights clarify molecular determinants of glucan solubility and hydration and provide a basis for designing glucan-based materials with tunable properties.