MD Calculations on Nystose Combined with NMR Spectroscopy on Inulin Related Oligosaccharides

Abstract

Molecular Dynamics (MD) calculations have been performed on nystose in water. According to these calculations the glycosidic linkages of the molecule are flexible. Structures obtained with MD calculations are compared with NMR data of several inulin related oligosaccharides and inulin, resulting in a model for the conformation of their fructofuranosyl residues. To extend the set of available NMR data of inulin related oligosaccharides, the complete assignment of the ¹H and ¹³C NMR signals of β-D-fructofuranosyl-(2->l)-ß-D-fructofuranosyl-(2->l)-ß-D-fructofuranosyl-(2->l)-ß-D-fructofuranosyl-(2->l)-α-D-glucopyranoside has been given here, using several 2D homo- and heteronuclear NMR experiments. Accurate coupling constants have been obtained by simulation of the 600 MHz 1D NMR spectra.     

Quantitative Analysis of the Molecular Weight Distribution of Inulin by Means of Anion Exchange HPLC with Pulsed Amperometric Detection

Abstract

A method, using anion exchange chromatography and pulsed amperometric detection, is described for quantitative analysis of the oligosaccharides present in inulin. The analysis of a number averaged and molecular weight averaged degree of polymerisation and the dispersion of inulin and inulin fractions is given.     

The Preparation and the Assignment of the 1H and 13C NMR Spectra of Methylated Derivatives of Inulin Oligosaccharides

Abstract

The complete assignment of the ¹H and ¹³C NMR spectra for permethylated sucrose, 1-kestose and nystose are given. Methylation of these inulin oligosaccharides did not change the conformation of the ring structures. A partially methylated derivative of nystose has been prepared using water as the solvent. The difference in reactivity of the various hydroxyl groups of nystose appeared to be very small.     

PMR and CMR spectroscopy of methyl 2,3,4,6-tetra-O-methyl-α- and -β-d-glucopyranoside : An application to the identification of partially methylated glucoses

The proton and ¹³C magnetic resonance spectra of methyl 2,3,4,6-tetra-O-methyl-α- and -β-d-glucopyranoside are completely assigned. For this purpose specific deuterium and ¹³C labelling, spin decoupling and spectrum simulation are employed. The NMR data are discussed and compared with those of the free monomers and the methylglucosides. A partially methylated glucose obtained as a degradation product in the permethylation analysis of a carbohydrate can be identified after permethylation of the compound with labelled Me groups and comparison of the PMR or CMR spectra with those of reference permethylglucoses. From these spectra information is obtained about type and ring form of the monomers and position(s) of the glycosidic bond(s) in the original oligo- or polysaccharide. The number of reference compounds necessary for identification is strongly reduced. The method can be extended to other monomers because there are significant differences between the NMR data of the various permethylmonosaccharides.     

Synthesis of Four Spacer-Containing Trisaccharides with the 4-0-(β-L-Rhamnopyranosyl)-D-glucopyranose Unit in Common,Representing Fragments of Capsular Polysaccharides from Streptococcus Pneumoniae Types 2, 7F, 22F,and 23F

Abstract

The synthesis is reported of 3-aminopropyl 3-O-[4-O(β-L-rhamnopyranosyl)-β-D-glucopyranosyl]-α-L-rhamnopyranoside (34), 3-aminopropyl 2-acetamido-3-O-[4-0-(β-L-rhamnopyranosyl)-β-D-glucopyranosyl]-2-deoxy-β-D-galactopyranoside (37), 3-aminopropyl 3-O-[4-O-(β-L-rhamnopyranosyl)-α-D-glucopyranosyl]-α-D-galactofuranoside (41), and 3-aminopropyl 4-O-[4-O-(β-L-rhamnopyranosyl)-β-D-glucopyranosyl]-β-D-galactopyranoside (45). These are spacer-containing fragments of the capsular polysaccharides of Streptococcus pneumoniae type 2, 7F, 22F, and 23F, respectively, which are constituents of Pneumovax^© 23. 2,3,4-Tri-O-benzyl-α-L-rhamnopyranosyl bromide was coupled to l,6-anhydro-2,3-di-(O-benzyl-β-D-glucopyranose (3). Opening of the anhydro ring, removal of AcO-1, and imidation of l,6-anhydro-2,3-di- O-benzyl-4-O-(2,3,4-tri-O-benzyl-β-L-rhamnopyranosyl)-β-D-glucopyranose (4β) afforded 6-O-acetyl-2,3-di-O-ben-zyl-4-O-(2,3,4-tri- O-benzyl-β-L-rhamnopyranosyl)-αβ-D-glucopyranosyl trichloroacet-imidate (7αβ). Condensation of 7αβ with 3-N-benzyloxycarbonylaminopropyl 2-O-ben-zyl-5,6-O-isopropylidene-α-D-galactofuranoside (26), followed by deprotection gave 41 Opening of the anhydro ring of 4 p followed by debenzylation, acerylauon, removal of AcO-1, and imidation yielded 2,3,6-tri-(9-aceryl-4-O-(2,3,4-tri-0-acetyl-P-L-rharnnopyran-.-osyl)-α-D-glucopyranosyl trichloroacetimidate (11). Condensation of 11 with 3-N-bcn-zyloxycarbonylaminopropyl 2,4-di-O-benzyl-α-L-rhamnopyranoside (18), with 3-N-bcn-zyloxycarbonylaminopropyl 2-acetamido-4,6-O-benzylidene-2-deoxy-β-D-galactopyran-oside (21), or with 3-N -benzyloxycarbonylaminopropyl 2-O-acetyl-3-O-allyl-6-O-benzyl-β-D-galactopyranoside (31), followed by deprotection afforded 34, 37, and 45, respectively.     

Synthesis and conjugation of oligosaccharide analogues of fragments of the immunoreactive glycan part of the circulating anodic antigen of the parasite Schistosoma mansoni

The gut-associated circulating anodic antigen (CAA) is one of the major excretory antigens produced by the parasite Schistosoma mansoni. The immunoreactive part of CAA is a threonine-linked polysaccharide composed of long stretches of the unique repeating disaccharide-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GalpNAc-(1-->. Previously, using surface plasmon resonance and ELISA techniques, it has been shown that some anti-CAA IgM monoclonal antibodies (MAbs) also recognize members of a series of bovine serum albumin (BSA)-coupled synthetic di- to penta-saccharide fragments of the CAA glycan. To generate information on the molecular level about the glycan specificity of the relevant IgM MAbs, two series of oligosaccharides related to the CAA disaccharide epitope were synthesized, and coupled to BSA. The first three analogues, beta-D-GlcpA-(1-->3)-[small beta]-D-GlcpNAc-(1-->O), beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GlcpNAc-(1-->O), and beta-D-GlcpA-(1-->3)-beta-D-GlcpNAc-(1-->6)-[beta-D-GlcpA-(1-->3)]-beta-D-GlcpNAc-(1-->O), wherein the native beta-D-GalpNAc moiety was replaced by beta-D-GlcpNAc, were synthesized to investigate the specificity of the selected MAbs to the carbohydrate backbone of CAA. The second series of analogues, beta-D-Glcp6S-(1-->3)-beta-D-GalpNAc-(1-->O), beta-D-GalpNAc-(1-->6)-[beta-D-Glcp6S-(1-->3)]-beta-D-GalpNAc-(1-->O), and beta-D-Glcp6S-(1-->3)-beta-D-GalpNAc-(1-->6)-[beta-D-Glcp6S-(1-->3)]-beta-D-GalpNAc-(1-->O), wherein the native beta-D-GlcpA moiety was replaced by beta-D-Glcp6S, was synthesized to evaluate the importance of the type/nature of the charge of CAA for the MAb recognition.     

Pattern recognition. An application to the identification of some stereoisomeric N-acetylhexosamines by mass spectrometry

A method is reported for the identification of trimethylsilylated stereoisomeric N-acetyl-hexosamines by application of a pattern recognition procedure to mass spectral data. The selection of characteristic mass spectral data and the pattern recognition procedure are discussed.