C(6)-oxidation followed by C(5)-epimerization of guar gum studied by high field NMR.
Biomacromolecules
; 5(2): 537-46, 2004.
Article
em En
| MEDLINE
| ID: mdl-15003018
ABSTRACT
Guar gum, a beta-D-(1-->4)-linked D-mannan with alpha-D-galactopyranosyl units attached as side groups, was treated with alpha-galactosidase, an enzyme that splits off the alpha-D-galactosyl units to obtain a galactomannan with a low galactose content. The galactose-depleted polysaccharide was then selectively oxidized in C(6) position and epimerized using mannuronan C(5)-epimerases, namely AlgE1, AlgE4, AlgE6, and their mixtures, obtaining new pseudo-alginates. In this paper, we report a full high field 1D and 2D NMR study of guar gum as such and of the galactose-depleted, oxidized and epimerized compounds, respectively. From the 1H NMR spectra, the degree of epimerization, the distribution of mannuronic acid (M) and guluronic acid (G) residues and the average G-block length, N(G>1), were obtained. By means of NMR diffusion experiments, it was also shown that no significant degradation of the polysaccharide occurs as a consequence of the epimerization reactions.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Ressonância Magnética Nuclear Biomolecular
/
Galactanos
/
Mananas
Idioma:
En
Ano de publicação:
2004
Tipo de documento:
Article