Systematic approach to the analysis of carbon 13 nmr spectra of complex carbohydrates 1. alpha d mannopyranosyl residues in oligo saccharides and their implications for studies of glyco proteins and glyco peptides
Allerhand, A.; Berman, E.
Journal of the American Chemical Society 106(8): 2400-2412
ISSN/ISBN: 0002-7863 Accession: 006573839
The 13C NMR spectra (at 67.9 MHz) and specific assignments of the 13C resonances are presented for Man.alpha.1 .fwdarw. 2Man, Man.alpha.1 .fwdarw. 2Man, Man.alpha.1 .fwdarw. 2Man.alpha.1 .fwdarw. 2Man.alpha.1 .fwdarw. 2Man, Man.alpha.1 .fwdarw. 3Man.alpha.1 .fwdarw. 2Man.alpha.1 .fwdarw. 2Man, Man.alpha.1 .fwdarw. 4Man.alpha.1 .fwdarw. OCH3, Man.alpha.1 .fwdarw. 6Man.alpha.1 .fwdarw. 6Man and the linear (1 .fwdarw. 6)-.alpha.-D-mannopyranan. The chemical shifts of all the carbons of a nonreducing .alpha.-D-mannopyranose residue are substantially influenced by the nature of the group to which the terminal residue is linked. For example, when going from a Man.alpha.1 .fwdarw. 4Man(.alpha.) moiety to Man.alpha.1 .fwdarw. 6Man(.alpha.), there are substantial changes in the chemical shifts of all carbons (except C-6) of the nonreducing terminal mannose. The .alpha.-D-mannosylation of an .alpha.- or .beta.-D-mannopyranosyl residue at C-2, C-3, C-4 or C-6 also causes significant changes in the chemical shifts of most carbons of the mannosylated residue. A method is presented for calculating the chemical shifts of any .alpha.-D-mannopyranosyl residue linked to other .alpha.-D-mannopyranosyl residues (at C-1, C-2, C-3, C-4 or C-6 or any combination of such linkages), on the basis of the chemical shifts of the oligosaccharides listed above. For this purpose, 2 sets of data are presented: the chemical shifts of nonreducing terminal .alpha.-D-mannopyranosyl residues involved in 1 .fwdarw. 2, 1 .fwdarw. 3, 1 .fwdarw. 4 and 1 .fwdarw. 6 linkages to other .alpha.-D-mannopyranosyl residues and the effects of .alpha.-D-mannosylation at C-2, C-3, C-4 and C-6 of an .alpha.-D-mannopyranosyl residue. The predictive powers of these 2 empirical data sets are tested by comparing the experimental and calculated spectra of the .alpha.-D-mannopyranosyl residues of Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 3)Man.alpha.1 .fwdarw. 6Man.beta.1 .fwdarw. R, where R = 4GlcNAc.beta.1 .fwdarw. 4GlcNAc.beta.1 .fwdarw. Asn. There is very good agreement between the experimental and calculated spectra, to the point that the calculated spectra are readily used to rule out alternate structures such as Man.alpha.1 .fwdarw. 6Man.alpha.1 .fwdarw. 6(Man.alpha.1 .fwdarw. 3)Man.beta.1 .fwdarw. R, on the basis of differences in several regions of the spectrum. High-field superconducting NMR spectrometers provide enough resolution in the 13C NMR spectra of complex carbohydrates to allow extensive use of the nonanomeric carbon resonances (and not just those of the anomeric carbons) in structural studies of large oligosaccharides.