A 1H and 13C NMR study of oligosaccharides from human milk. Application of the computer program CASPER

Several oligosaccharides from human milk, containing vicinally branched residues, have been analysed with respect to induced NMR chemical shift changes that originate from the branching. Two types of branching were investigated: (i) linear oligosaccharides with a 2-linked residue, which thus becomes vicinally 1,2-disubstituted, and (ii) oligosaccharides with either 2,3- or 3,4-branching. It could be concluded that, in 13C NMR spectra of the first type, for which only moderately sized induced changes (< 2 ppm) had been observed previously, large (> 5 ppm) changes are also present. For 2,3- and 3,4-branching, changes similar to those observed earlier were found. In 1H NMR spectra, significant induced shifts for signals from anomeric, aglyconic, and H-5 protons were observed. For most trisaccharides, a unique set of values for the chemical shift differences was found, thus making it suitable to use them for characterisation of substitution patterns in the analysis with the computer program CASPER.