HIGH-FIELD NMR-SPECTROSCOPY OF PARTIALLY N-DEACETYLATED CHITINS (CHITOSANS)
.1. DETERMINATION OF THE DEGREE OF N-ACETYLATION AND THE DISTRIBUTION
OF N-ACETYL GROUPS IN PARTIALLY N-DEACETYLATED CHITINS (CHITOSANS)
BY HIGH-FIELD NMR-SPECTROSCOPY
Carbohydr. Res., 211 (1):
17 -- 23 (апреля 1991)Аннотация
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 H-1-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-GlcNc 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.