1H and 15N NMR analyses on heparin, Heparan sulfates and related monosaccharides concerning the chemical exchange regime of the N-Sulfo-glucosamine sulfamate proton

Abstract

Heparin and heparan sulfate are structurally related glycosaminoglycans (GAGs). Both GAGs present, although in different concentrations, N-sulfo-glucosamine (GlcNS) as one of their various composing units. The conditional fast exchange property of the GlcNS sulfamate proton in these GAGs has been pointed as the main barrier to its signal detection via NMR experiments, especially1H-15N HSQC. Here, a series of NMR spectra is collected on heparin, heparan sulfate and related monosaccharides. The N-acetyl glucosamine-linked uronic acid types of these GAGs were properly assigned in the1H-15N HSQC spectra. Dynamic nuclear polarization (DNP) was employed in order to facilitate 1D spectral acquisition of the sulfamate15N signal of free GlcNS. Analyses on the multiplet pattern of scalar couplings of GlcNS15N has helped to understand the chemical properties of the sulfamate proton in solution. The singlet peak observed for GlcNS happens due to fast chemical exchange of the GlcNS sulfamate proton in solution. Analyses on kinetics of alpha-beta anomeric mutarotation via1H NMR spectra have been performed in GlcNS as well as other glucose-based monosaccharides. 1D1H and 2D1H-15N HSQC spectra recorded at low temperature for free GlcNS dissolved in a proton-rich solution showed signals from all exchangeable protons, including those belonging to the sulfamate group. This work suits well to the current grand celebration of one-century-anniversary of the discovery of heparin.