Chemical preparation and structural characterization of a homogeneous series of chitin/chitosan oligomers.
The preparation of a homogeneous series of chitin/chitosan oligomers (chito-oligomers) with the same distribution of degrees of polymerization (DP) ranging from 2 to 12, but with various average degrees of N-acetylation (DA) from 0 to 90% is described. This DA-series was obtained according to a two-step chemical process involving (i) the production of a well-defined mixture of glucosamine (GlcN) oligomers obtained by acid hydrolysis of a fully N-deacetylated chitosan and after selective precipitations of the hydrolysis products, and (ii) the partial N-acetylation of the GlcN units of these oligomers from a hydro-alcoholic solution of acetic anhydride in a controlled manner. The characterization of this series of samples with different DAs by proton nuclear magnetic resonance (1H NMR) spectroscopy and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) allowed us to determine their average DA and identify the main oligomer structures constituting each mixture. Furthermore, MALDI-TOF MS was particularly helpful to study the distribution evolution of the diverse oligomers as a function of DA for the main DPs from 3 to 7. The modeling of these distributions by means of a binomial law displayed that the chemical N-acetylation of low DP GlcN oligomers, produced in a homogeneous medium, occurs randomly along the oligosaccharide chains in accordance with a statistical (Bernoullian) arrangement. In this case, the relative proportion of each chito-oligomer present in the mixture can be estimated precisely as a function of DA considering oligomers of same DP.
Trombotto
Stéphane
S
Laboratoire des Matériaux Polymères et des Biomatériaux, UMR CNRS 5223 Ingénierie des Matériaux Polymères, Université Claude Bernard Lyon 1, Domaine scientifique de La Doua, Bâtiment ISTIL, Villeurbanne Cedex, France. stephane.trombotto@univ-lyon1.fr
Ladavière
Catherine
C
Delolme
Frédéric
F
Domard
Alain
A
D000107:Acetylation; D002236:Carbohydrate Conformation; D002686:Chitin / Q000138:chemical synthesis / Q000737:chemistry*; D048271:Chitosan / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D009844:Oligosaccharides / Q000138:chemical synthesis / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D009844:Oligosaccharides; D002686:Chitin; D048271:Chitosan