The crystal structure of chitin and chitosan

Mogilevskaya, E. L.; Акопова, Т. А.; Зеленецкий, А. Н.; Ozerin, А. N.

doi:10.1134/s0965545x06020039

Cited by 92 publications

(69 citation statements)

References 20 publications

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“…14 In the solid state, chitosan is characterized by an ordered fibrillar structure with high degree of crystallinity, and polymorphism. 11,15 According to X-ray crystallography experiments, chitosans have anhydrous and hydrated forms with piles of chains arranged in an anti-parallel fashion. [16][17][18][19] In its linear form, this polysaccharide has four main helical forms: a two-…”

Section: Introductionmentioning

confidence: 99%

Chitosan molecular structure as a function of N‐acetylation

2011

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Molecular dynamics simulations have been carried out to characterize the structure and solubility of chitosan nanoparticle-like structures as a function of the deacetylation level (0, 40, 60, and 100%) and the spatial distribution of the N-acetyl groups in the particles. The polysaccharide chains of highly N-deacetylated particles where the N-acetyl groups are uniformly distributed present a high flexibility and preference for the relaxed two-fold helix and five-fold helix motifs. When these groups are confined to a given region of the particle, the chains adopt preferentially a two-fold helix with ϕ and ψ values close to crystalline chitin. Nanoparticles with up to 40% acetylation are moderately soluble, forming stable aggregates when the N-acetyl groups are unevenly distributed. Systems with 60% or higher N-acetylation levels are insoluble and present similar degrees of swelling regardless the distribution of their N-acetyl groups. Overall particle solvation is highly affected by electrostatic forces resulting from the degree of acetylation. The water mobility and orientation around the polysaccharide chains affects the stability of the intramolecular O3-HO3((n)) ···O5((n +) (1)) hydrogen bond, which in turn controls particle aggregation.

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Section: Introductionmentioning

confidence: 99%

Chitosan molecular structure as a function of N‐acetylation

2011

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“…The diversity of chitosan structural types depend on the experimental conditions (kind and concentration of acid, temperature and salt preparation) used for the conversion of chitin into chitosan [128]. The helical structure propensities can be determined according to the repeating unit and helical symmetry as observed in chitosan crystal structures [121,123,128,130,131]. A less common motif, classified as 3-fold, has also been identified ( Figure 2B).…”

Section: Chitosan Molecular Structurementioning

confidence: 99%

“…In the solid state, chitosan is characterized by an ordered fibrillar structure with a high degree of crystallinity, and polymorphism [120,121]. X-ray measurements of the chitosan polymer have shown an extended two-fold helix in a zigzag structure [122,123].…”

Section: Chitosan Molecular Structurementioning

confidence: 99%

“…A type II salt variant, called Type IIa, has a similar fiber repeat (4.05 nm), but with an asymmetric unit consisting of a glucosamine dimer in a 4/1 helical symmetry. This right-handed helix comprised of four asymmetric subunits is classified as 4/1-helix conformation, being also called four-fold helix ( Figure 2C) [121,129]. The most recently discovered type III form has a chain repeat of 2.55 nm, a 5/3 helical symmetry, and an asymmetric unit of a single glucosamine residue.…”

Section: Chitosan Molecular Structurementioning

confidence: 99%

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The Molecular Structure and Conformational Dynamics of Chitosan Polymers: An Integrated Perspective from Experiments and Computational Simulations

Cunha¹,

Soares²,

Rusu³

et al. 2012

The Complex World of Polysaccharides

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“…In chitin, the degree of acetylation (DA) is > 50 % indicating the presence of some amino groups in its structure (C-2) since some deacetylation might take place during extraction. When the degree of acetylation is < 50 % it is regarded as chitosan [4].…”

Section: Introductionmentioning

confidence: 99%

Effect of Acid Hydrolysis on Tableting Properties of Chitin Obtained from Shrimp Heads

Rojas¹,

Madrigal²,

Ortiz³

2015

Trop. J. Pharm Res

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Purpose: To assess the effect of acid hydrolysis on the degree of acetylation, crystallinity, and molecular weight of chitin obtained from shrimp heads as well as to evaluate their tableting properties. Methods: The effect of acid hydrolysis conditions such as reaction temperature (46, 60, 80, 100, 114°C), hydrochloric acid concentration (4.6, 6, 8, 10 and 11.4 M) and reaction time (0.6, 2, 4, 6 and 7.4 h) were examined. The degree of acetylation and molecular weight were found by Fourier transform spectroscopy (FT-IR) and viscometry methods, respectively. The degree of crystallinity degree and its compact tensile strength were determined by x-ray and Fell & Newton methods, respectively. Results: The combined effect of high temperature (> 80 o C), HCl concentration (> 2 M) and reaction time (> 4 h) led to high depolymerization, reduction in degree of

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The crystal structure of chitin and chitosan

Cited by 92 publications

References 20 publications

Chitosan molecular structure as a function of N‐acetylation

Chitosan molecular structure as a function of N‐acetylation

The Molecular Structure and Conformational Dynamics of Chitosan Polymers: An Integrated Perspective from Experiments and Computational Simulations

Effect of Acid Hydrolysis on Tableting Properties of Chitin Obtained from Shrimp Heads

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