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.
The composition and sequence of 2-acetamido-2-deoxy-beta-D-glucose (GlcNAc) and 2-amino-2-deoxy-beta-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 homogeneous 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 degree of acetylation of 50% were soluble at neutral pH.
Vårum
K M
KM
Norwegian Biopolymer Laboratory (NOBIPOL), Division of Biotechnology, Norwegian Institute of Technology, University of Trondheim.
Anthonsen
M W
MW
Grasdalen
H
H
Smidsrød
O
O
D000107:Acetylation; D002240:Carbohydrate Sequence; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry; D048271:Chitosan; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data
D002686:Chitin; D048271:Chitosan