Determination of the degree of N-acetylation and the distribution of N-acetyl groups in partially N-deacetylated chitins (chitosans) by high-field n.m.r. spectroscopy
1991; Elsevier BV; Volume: 211; Issue: 1 Linguagem: Inglês
10.1016/0008-6215(91)84142-2
ISSN1873-426X
AutoresKjell M. Vårum, Marit W. Antohonsen, Hans Grasdalen, Olav Smidsrød,
Tópico(s)Enzyme Production and Characterization
ResumoThe composition and sequence of 2-acetamino-2-deoxy-β-d-glucose (GlcNAc) and 2-amino-2-deoxy-β-d-glucose (GlcN) residues in partially N-deacetylated chitosans, prepared under homogeneous and heterogeneous conditions, have been determined by 1H-n.m.r. spectroscopy. It was necessary to depolymerise the chitosan slightly by treatment with nitrous acid before spectroscopy. A sequence-dependent deshielding of H-1 of the GlcNAc residues made it possible to determine the proportions of the four possible diads. Chitosan prepared by N-deacetylation under homogenous conditions gave values for the diad frequencies that were roughly consistent with a random distribution of the N-acetyl groups. Samples prepared under heterogeneous conditions have a frequency of the GlcNAc-GlcNAc diad slightly higher than for a random (Bernoullian) distribution. The chitosans, prepared under both homogeneous and heterogeneous conditions, with a degre eof acetylation of 50% were soluble at neutral pH.
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