Characterization of chitin and chitosan molecular structure in aqueous solution

Eduardo F. Franca; Roberto D. Lins; Luiz C.G. Freitas; T. P. Straatsma

doi:10.1021/ct8002964

Characterization of chitin and chitosan molecular structure in aqueous solution

Eduardo F. Franca, Roberto D. Lins, Luiz C.G. Freitas, T. P. Straatsma

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Abstract

Molecular dynamics simulations have been used to characterize the structure of single chitin and chitosan chains in aqueous solutions. Chitin chains, whether isolated or in the form of a ß-chitin nanoparticle, adopt the 2-fold helix with φ and φ values similar to its crystalline state. In solution, the intramolecular hydrogen bond HO3_(n)-...O5 _(n+1) responsible for the 2-fold helical motif in these polysaccharides is stabilized by hydrogen bonds with water molecules in a well-defined orientation. On the other hand, chitosan can adopt five distinct helical motifs, and its conformational equilibrium is highly dependent on pH. The hydrogen bond pattern and solvation around the O3 atom of insoluble chitosan (basic pH) are nearly identical to these quantities in chitin. Our findings suggest that the solubility and conformation of these polysaccharides are related to the stability of the intrachain H03_(n)...05 _(n+1) hydrogen bond, which is affected by the water exchange around the O3-HO3 hydroxyl group.

Original language	English
Pages (from-to)	2141-2149
Number of pages	9
Journal	Journal of Chemical Theory and Computation
Volume	4
Issue number	12
DOIs	https://doi.org/10.1021/ct8002964
State	Published - Dec 9 2008
Externally published	Yes

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title = "Characterization of chitin and chitosan molecular structure in aqueous solution",

abstract = "Molecular dynamics simulations have been used to characterize the structure of single chitin and chitosan chains in aqueous solutions. Chitin chains, whether isolated or in the form of a {\ss}-chitin nanoparticle, adopt the 2-fold helix with φ and φ values similar to its crystalline state. In solution, the intramolecular hydrogen bond HO3(n)-...O5 (n+1) responsible for the 2-fold helical motif in these polysaccharides is stabilized by hydrogen bonds with water molecules in a well-defined orientation. On the other hand, chitosan can adopt five distinct helical motifs, and its conformational equilibrium is highly dependent on pH. The hydrogen bond pattern and solvation around the O3 atom of insoluble chitosan (basic pH) are nearly identical to these quantities in chitin. Our findings suggest that the solubility and conformation of these polysaccharides are related to the stability of the intrachain H03(n)...05 (n+1) hydrogen bond, which is affected by the water exchange around the O3-HO3 hydroxyl group.",

author = "Franca, {Eduardo F.} and Lins, {Roberto D.} and Freitas, {Luiz C.G.} and Straatsma, {T. P.}",

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T1 - Characterization of chitin and chitosan molecular structure in aqueous solution

AU - Franca, Eduardo F.

AU - Lins, Roberto D.

AU - Freitas, Luiz C.G.

AU - Straatsma, T. P.

PY - 2008/12/9

Y1 - 2008/12/9

N2 - Molecular dynamics simulations have been used to characterize the structure of single chitin and chitosan chains in aqueous solutions. Chitin chains, whether isolated or in the form of a ß-chitin nanoparticle, adopt the 2-fold helix with φ and φ values similar to its crystalline state. In solution, the intramolecular hydrogen bond HO3(n)-...O5 (n+1) responsible for the 2-fold helical motif in these polysaccharides is stabilized by hydrogen bonds with water molecules in a well-defined orientation. On the other hand, chitosan can adopt five distinct helical motifs, and its conformational equilibrium is highly dependent on pH. The hydrogen bond pattern and solvation around the O3 atom of insoluble chitosan (basic pH) are nearly identical to these quantities in chitin. Our findings suggest that the solubility and conformation of these polysaccharides are related to the stability of the intrachain H03(n)...05 (n+1) hydrogen bond, which is affected by the water exchange around the O3-HO3 hydroxyl group.

AB - Molecular dynamics simulations have been used to characterize the structure of single chitin and chitosan chains in aqueous solutions. Chitin chains, whether isolated or in the form of a ß-chitin nanoparticle, adopt the 2-fold helix with φ and φ values similar to its crystalline state. In solution, the intramolecular hydrogen bond HO3(n)-...O5 (n+1) responsible for the 2-fold helical motif in these polysaccharides is stabilized by hydrogen bonds with water molecules in a well-defined orientation. On the other hand, chitosan can adopt five distinct helical motifs, and its conformational equilibrium is highly dependent on pH. The hydrogen bond pattern and solvation around the O3 atom of insoluble chitosan (basic pH) are nearly identical to these quantities in chitin. Our findings suggest that the solubility and conformation of these polysaccharides are related to the stability of the intrachain H03(n)...05 (n+1) hydrogen bond, which is affected by the water exchange around the O3-HO3 hydroxyl group.

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Characterization of chitin and chitosan molecular structure in aqueous solution

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