NMR analysis of conformationally dependent nJC,H and nJC,C in the trisaccharide α-L-Rhap-(1→2)[α-L-Rhap-(1→3)]-α-L-Rhap-OMe and a site-specifically labeled isotopologue thereof
2011 (English)In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 49, no 3, 117-124 p.Article in journal (Refereed) Published
An array of NMR spectroscopy experiments have been carried out to obtain conformationally dependent 1H,13C- and 13C,13C-spin–spin coupling constants in the trisaccharide α-L-Rhap-(1 → 2)[α-L-Rhap-(1 → 3)]-α-L-Rhap-OMe. The trisaccharide was synthesized with 13C site-specific labeling at C2′ and C2″, i.e. in the rhamnosyl groups in order to alleviate 1H spectral overlap. This facilitated the measurement of a key trans-glycosidic proton–proton cross-relaxation rate using 1D 1H,1H-T-ROESY experiments as well as a 3JC, H coupling employing 1D 1H,13C-long-range experiments, devoid of potential interference from additional J coupling. By means of both the natural abundance compound and the 13C-labeled sample 2D 1H,13C-J-HMBC and 1H,13C-HSQC-HECADE NMR experiments, total line-shape analysis of 1H NMR spectra and 1D 13C NMR experiments were employed to extract 3JC, H, 2JC, H, 3JC, C, and 1JC, C coupling constants. The 13C site-specific labeling facilitates straightforward determination of nJC, C as the splitting of the 13C natural abundance resonances. This study resulted in eight conformationally dependent coupling constants for the trisaccharide and illustrates the use of 13C site-specific labeling as a valuable approach that extends the 1D and 2D NMR methods in current use to attain both hetero- and homonuclear spin–spin coupling constants that subsequently can be utilized for conformational analysis.
Place, publisher, year, edition, pages
2011. Vol. 49, no 3, 117-124 p.
J-HMBC, HSQC-HECADE, HETCOR, oligosaccharide, heteronuclear long-range coupling constants, modified J-doubling
IdentifiersURN: urn:nbn:se:su:diva-55134DOI: 10.1002/mrc.2723ISI: 000287890600004OAI: oai:DiVA.org:su-55134DiVA: diva2:401373
FunderSwedish Research CouncilKnut and Alice Wallenberg Foundation