ʹChair–boatʹ transitions and side groups affect the stiffness of polysaccharides

Atomic force microscopy experiments with individual β-(1,4)-glucose polymers (cellulose) and α-(1,4)-glucose polymers (amylose) have been simulated by molecular dynamics stretching simulations, and force/extension curves were calculated. For forces above 1200 pN, we predict a stiffness of 5100 pN/Å for both polymers. In contrast to β-glucose, α-glucose exhibits increased flexibility in the 300–1200 pN range, which our simulations attribute to conformational `chair-boatʹ transitions of the α-glucose monomers. For β-glucose no such transitions were seen. We suggest a mechanism of neighbor inhibition, which should allow the tailoring of elastic properties through modification of inter-monomeric rotational flexibility, e.g., by introducing or removing bulky or charged side groups.