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Studies of crystalline native celluloses using potential energy calculations
Authors:Alvo Aabloo  Alfred D. French  Raik-Hiio Mikelsaar  Aleksandr J. Pertsin
Affiliation:(1) Institute of Experimental Physics and Technology, University of Tartu, Tähe 4 Street, EE2400 Tartu, Estonia;(2) Southern Regional Research Center, US Department of Agriculture, 1100 Robert E. Lee Blvd, PO Box 19687, 70179 New Orleans, LA, USA;(3) Institute of General and Molecular Pathology, University of Tartu, Veski 35 Street, EE2400 Tartu, Estonia;(4) Institute of Element-Organic Compounds, Vavilova 28 Street, GSP1, V-334, 117813 Moscow, Russia
Abstract:Energies for various trial packing arrangements of unit cells for the Iagr and Ibeta phases of native cellulose discovered by Sugiyamaet al. were evaluated. Both a rigid-ring method, PLMR, and the full-optimization, molecular mechanics program, MM3(90), were used. For both phases the models that had the lowest PLMR energy also had the lowest MM3 energy. Both calculated models have the chains packed lsquouprsquo, O6s intg positions, and the same sheets of hydrogen-bonded chains. The Ibeta structure model is essentially identical to that proposed previously for ramie cellulose by Woodcock and Sarko. It is also the same as the best parallel model previously proposed that was based on the X-ray data of Mann, Gonzalez and Wellard, once the various unit cell conventions are considered. Also, the energies from both methods for all three celluloses, Iagr, Ibeta and II, are in the order that rationalizes their relative stabilites.
Keywords:cellulose I  molecular mechanics  crystal structure  molecular  modelling
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