Abstract
Heparin and heparan sulfate (HS) are members of a biologically important group of highly anionic linear polysaccharides called glycosaminoglycans (GAGs). Because of their structural complexity, the molecular-level characterization of heparin and HS continues to be a challenge. The work presented herein describes an emerging approach for the analysis of unfractionated and low molecular weight heparins, as well as porcine and human-derived HS. This approach utilizes the untapped potential of (15)N NMR to characterize these preparations through detection of the NH resonances of N-sulfo-glucosamine residues. The sulfamate group (1)H and (15)N chemical shifts of six GAG microenvironments were assigned based on the critical comparison of selectively modified heparin derivatives, NMR measurements for a library of heparin-derived oligosaccharide standards, and an in-depth NMR analysis of the low molecular weight heparin enoxaparin through systematic investigation of the chemical exchange properties of NH resonances and residue-specific assignments using the [(1)H,(15)N] HSQC-TOCSY experiment. The sulfamate microenvironments characterized in this study include GlcNS(6S)-UA(2S), ΔUA(2S)-GlcNS(6S), GlcNS(3S)(6S)-UA(2S), GlcNS-UA, GlcNS(6S)-red(α), and 1,6-anhydro GlcNS demonstrating the utility of [(1)H,(15)N] HSQC NMR spectra to provide a spectroscopic fingerprint reflecting the composition of intact GAGs and low molecular weight heparin preparations.