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Sanders_etal_2020_amorphous_starch_preprint_rev02.pdf (2.06 MB)

Characterizing Moisture Uptake and Plasticization Effects of Water on Amorphous Amylose Starch Models Using Molecular Dynamics Methods

preprint
revised on 02.07.2020 and posted on 03.07.2020 by Jeffrey Sanders, Mayank Misra, Thomas JL Mustard, David J. Giesen, Teng Zhang, John Shelley, Mathew D. Halls

Dynamics and thermophysical properties of amorphous starch were explored using molecular dynamics (MD) simulations. Using the OPLS3e force field, simulations of short amylose chains in water were performed to determine force field accuracy. Using well-tempered metadynamics, a free energy map of the two glycosidic angles of an amylose molecule was constructed and compared with other modern force fields. Good agreement of torsional sampling for both solvated and amorphous amylose starch models was observed. Using combined grand canonical Monte Carlo (GCMC)/MD simulations, a moisture sorption isotherm curve is predicted along with temperature dependence. Concentration-dependent activation energies for water transport agree quantitatively with previous experiments. Finally, the plasticization effect of moisture content on amorphous starch was investigated. Predicted glass transition temperature (Tg) depression as a function of moisture content is in line with experimental trends. Further, our calculations provide a value for the dry Tg for amorphous starch, a value which no experimental value is available.


History

Email Address of Submitting Author

jeffrey.sanders@schrodinger.com

Institution

Schrödinger Inc

Country

United States

ORCID For Submitting Author

0000-0003-3279-2850

Declaration of Conflict of Interest

All authors are employed by Schrödinger Inc.

Version Notes

Revision 01: corrected error in figure 3. Revision 02: Replaced low resolution figures with higher resolution ones.

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