CHAPTER 10: Analysis of Glycosaminoglycans by ¹⁵N-NMR Spectroscopy

Glycosaminoglycans (GAGs) are sulfated polysaccharides of complex structure endowed with multiple biomedical functions. Liquid-state 1D and 2D nuclear magnetic resonance (NMR) spectroscopy has been the analytical technique mostly employed in structural characterization of GAGs. Analyses have been performed primarily on ¹H and ¹³C nuclei of anomeric and ring atoms. Nowadays, however, another isotope type, ¹⁵N from the composing amino sugars (hexosamine units), was proven to be also quite useful for analyses. The recent developments for enhancing NMR sensitivity such as the advent and spread of high magnetic fields, cryoprobe technology, isotopic labeling techniques, and novel 2D pulse sequences have been the principal factors to allow the progress of the ¹⁵N-based NMR structural analyses of GAGs. Despite the low abundance and sensitivity of ¹⁵N together with the few resultant ¹⁵N-related cross-peaks seen in the 2D spectra of GAGs, a big set of structural information can still be retrieved from the ¹⁵N–NMR analyses. This chapter aims therefore at describing this new set of structural information.