C6-oxidation and c5-epimerization of locust bean galactomannan studied by high field NMR and circular dichroism.
Galactose depleted locust bean gum was selectively oxidized in C(6) position and epimerized with mannuronan C(5)-epimerases to obtain the corresponding artificial uronanes. These new pseudo-alginates were characterized by NMR spectroscopy and circular dichroism (CD). Specifically, 1D and 2D NMR techniques allowed the degree of epimerization, the distribution of mannuronic and guluronic acid residues in the polysaccharidic chain, and the average G block length to be determined. In addition, NMR diffusion experiments showed that the epimerization reaction did not significantly degrade the polysaccharidic chains. Circular dichroism was used to investigate the kinetics of the epimerization reaction and to evidence the specific interaction between the epimerized locust bean samples with Ca(II) ions in dilute solution. All of the samples considered in this study form wall to wall gels in concentrated polymer solutions.
Dentini
Mariella
M
Department of Chemistry, University of Rome La Sapienza, Rome, Italy. mariella.dentini@uniroma1.it
Caucci
Daniele
D
Barbetta
Andrea
A
Crescenzi
Vittorio
V
Skjåk-Braek
Gudmund
G
Capitani
Donatella
D
Mannina
Luisa
L
Viel
Stéphane
S
D000045:Acacia / Q000737:chemistry*; D002118:Calcium / Q000737:chemistry; D002236:Carbohydrate Conformation; D002942:Circular Dichroism; D005690:Galactose / Q000031:analogs & derivatives; D005782:Gels / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008351:Mannans / Q000737:chemistry* / Q000378:metabolism; D010084:Oxidation-Reduction; D012639:Seeds / Q000737:chemistry*; D012996:Solutions; D013237:Stereoisomerism; D013379:Substrate Specificity
D005782:Gels; D007477:Ions; D008351:Mannans; D012996:Solutions; C012990:galactomannan; D002118:Calcium; D005690:Galactose