Elucidating Salt Effects on Chitosan Dynamics

Using molecular dynamics simulations, we explored the solution salt effect on the conformational dynamics of chitosan chains. Our data revealed that the chitosan glycosidic bonds can rotate to an extended syn and the so-called anti-Ψ conformations. Interestingly, added salt increases the latter population and consequently backbone bending and flexibility. For the charged chain salt weakens charge-charge repulsion that favors the extended state, while for the neutral chain, salt disrupts an intramolecular hydrogen bond that stabilizes the extended state. These data suggest that salt concentration modulates the conformation and dynamics of individual chitosan chains in addition to intermolecular hydrogen bonding during pH-induced self assembly. This work provides a significant step towards understanding the complex environmental control of chitosan’s hydrogel properties which cannot be accessed experimentally.

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