Preparation and characterisation of chitosans with oligosaccharide branches.
The trimer 2-acetamido-2-deoxy-D-glucopyranosyl-beta-(1-->4)-2-acetamido-2-deoxy-D-glucopyranosyl-beta-(1-->4)-2,5-anhydro-D-mannofuranose (A-A-M) was reductively N-alkylated onto a fully de-N-acetylated chitosan (F(A)<0.001, DP(n)=25) to obtain branched chitosans with degree of substitution (DS) of 0.070, 0.23 and 0.40, as determined by 1H NMR spectroscopy. The apparent pK(a) values of the primary and secondary amines of the chitosans substituted with the trimer A-A-M were determined by monitoring the chemical shift of the H-2 of GlcN, and were determined as 6.5-6.9 for the primary (unsubstituted) amines and as 5.0-5.2 for the secondary (substituted) amines. The intrinsic pK(a) values (pK(int)) were found to be 7.3-7.4 for the substituted and 8.7 for the unsubstituted amines. The chitosan branched with A-A-M (DS 0.40) was found to be soluble in aqueous solution over the entire pH range. SEC-MALLS (size-exclusion chromatography with a multi-angle laser light scattering detector) further showed that addition of branches did not affect the molar hydrodynamic volume of the chitosan.
Tømmeraas
Kristoffer
K
Norwegian Biopolymer Laboratory (NOBIPOL), Department of Biotechnology, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway.
Köping-Höggård
Magnus
M
Vårum
Kjell M
KM
Christensen
Bjørn E
BE
Artursson
Per
P
Smidsrød
Olav
O
D000606:Amino Sugars; D002686:Chitin / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry; D048271:Chitosan; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D025942:Oligosaccharides, Branched-Chain / Q000138:chemical synthesis* / Q000737:chemistry; D012212:Rheology; D012995:Solubility; D014312:Trisaccharides / Q000737:chemistry
D000606:Amino Sugars; D025942:Oligosaccharides, Branched-Chain; D014312:Trisaccharides; D002686:Chitin; D048271:Chitosan