Molecular dynamics approach to study the discrepancies in the thermal behavior of amylose and chitosan conformations

Tetsuya Sakajiri, Takeshi Kikuchi, I. Simon, Katsumi Uchida, Takaki Yamamura, Tadahiro Ishii, Hirofumi Yajima

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

A unique discrepancy in the thermal behavior exists between two species of linear polysaccharides of amylose with of α(1→4) linked d-glucan and of chitosan with β(1→4) linked d-glucosamine. Amylose and chitosan display thermal non-hysteresis and hysteresis phenomena, respectively. Amylose forms a blue-colored complex with iodine. Heating this complex to high temperatures causes the color disappear, and the complex turns white. After annealing the material, the blue color is restored. This behavior is different from that of another carbohydrate, chitosan. Chitosan forms a purple-colored complex with iodine. The color of the chitosan-iodine complex also disappears at high temperatures; however, the purple color is not restored after annealing. To explain the discrepancy in the thermal behavior between the two polysaccharides, molecular dynamics (MD) calculations were carried out to probe the effect of heating and annealing on amylose and chitosan conformations. The 12-mer oligosaccharide chains were used as a reference, and a wide exploration of the potential surfaces of both oligosaccharide 6-mers was made investigated under the restriction of a given end-to-end distance. For the amylose chain, it was predicted that amylose assumes a helical conformation as the lowest-energy structure at the bottom of a smooth-sided potential energy well. Therefore, the random coil structure of the amylose chain at high temperature can be restored to helical structure by annealing. On the other hand, chitosan was predicted to have a rugged shape potential energy surface, in which the difference between the energy values of the crystalline-like extended and hairpin conformations is small, but with a significant energy barrier between the two conformational states. The latter characteristics of chitosan result in a thermal hysteresis effect due to a long-term occupation of the trapped states at one of the hairpin conformations in the annealing process.

Original languageEnglish
Pages (from-to)133-140
Number of pages8
JournalJournal of Molecular Structure: THEOCHEM
Volume764
Issue number1-3
DOIs
Publication statusPublished - May 30 2006

Fingerprint

Amylose
Chitosan
Molecular Dynamics Simulation
Conformations
Molecular dynamics
Hot Temperature
molecular dynamics
annealing
iodine
color
polysaccharides
Annealing
Color
Iodine
Oligosaccharides
potential energy
hysteresis
Polysaccharides
heating
Heating

Keywords

  • Amylose
  • Chitosan
  • Molecular dynamics
  • Thermal hysteresis

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Computational Theory and Mathematics
  • Atomic and Molecular Physics, and Optics

Cite this

Molecular dynamics approach to study the discrepancies in the thermal behavior of amylose and chitosan conformations. / Sakajiri, Tetsuya; Kikuchi, Takeshi; Simon, I.; Uchida, Katsumi; Yamamura, Takaki; Ishii, Tadahiro; Yajima, Hirofumi.

In: Journal of Molecular Structure: THEOCHEM, Vol. 764, No. 1-3, 30.05.2006, p. 133-140.

Research output: Contribution to journalArticle

Sakajiri, Tetsuya ; Kikuchi, Takeshi ; Simon, I. ; Uchida, Katsumi ; Yamamura, Takaki ; Ishii, Tadahiro ; Yajima, Hirofumi. / Molecular dynamics approach to study the discrepancies in the thermal behavior of amylose and chitosan conformations. In: Journal of Molecular Structure: THEOCHEM. 2006 ; Vol. 764, No. 1-3. pp. 133-140.
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