Dispersing the crowd: Adopting 13C direct detection for glycans

• Published in: Journal of magnetic resonance (1997) Vol. 318; p. 106792
• Main Authors: Battistel, Marcos D., Freedberg, Darón I.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-09-2020
• Subjects: 13C direct detection; Carbohydrates; Cellobiose; Constant time; Glycans; Low-gamma nuclei; Natural abundance; Oligosaccharide; Pure shift; Resolution; Sialic acid; Sialyl Lewis X; SMILE; TOCSY; 13C direct detection; Carbohydrates; Sialic acid; Natural abundance; Oligosaccharide; Constant time; Sialyl Lewis X; Glycans; TOCSY; Pure shift; Low-gamma nuclei; Cellobiose; SMILE; Resolution
• ISSN: 1090-7807; 1096-0856
• DOI: 10.1016/j.jmr.2020.106792

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•2D with direct detection of 13C in natural abundance improves resolution in glycan spectra.•Uses a fraction of the time compared to conventional methods.•Suppressing 1H-1H coupling further improves 2D spectral resolution.•Strategy can be applied to other oligo- and polymers.•Complete resolution of highly degenerate glycan spectra.
As a direct consequence of technological advancements, the interest in direct detection of low-gamma/low-sensitivity heteronuclei for NMR experiments has been revived. Until recently, experimental development of 13C/15N detected experiments has been focused on protein NMR. In the present report, we extend the use of 13C-detected experiments to structural studies of glycans in natural abundance. The narrow 1H and wider 13C signal dispersion make glycans ideal candidates for heteronuclear detection. We show that 13C-detected HSQC offers a ten-fold increase in 13C dimension resolution compared to the analogous 1H-detected HSQC, when the experiments are acquired for the same amount of time. The enhanced resolution comes at the expense of 2 to 3-fold loss in SNR; however, the observed signal loss is a fraction of the theoretical 8-fold difference expected between experiments. Further, we show that by combining a 1H constant time element (CT), SMILE data reconstruction and 13C-direct detection, complete resonance assignments of highly degenerate glycan signals are possible. Finally, we demonstrate the potential of our strategy to aid in the assignment of complex glycans, by using a novel 13C-detected version of the CT-HSQC-TOCSY experiment performed on sialyl Lewis X pentasaccharide model system.