Figure 2.

NMR analyses of magnesium chloride modified heparin: (a) Comparison of a portion of 1D ¹H NMR spectra of heparin (I), heparin–Mg²⁺ (II), and heparin–Ca²⁺ (III) acquired in 99.95% D₂O at 37 °C. Proton chemical shift assignment of iduronic acid, and glucosamine, residues are shown on top of each resonance. (IV) Bar plot showing ¹H chemical shift perturbation of heparin in the presence of Mg²⁺ and Ca²⁺. ¹H chemical shift difference between heparin–M²⁺ (M = Mg, Ca) and heparin are presented on the y-axis. Positive value indicates the deshielding of respective protons in the presence of M²⁺ (M = Mg, Ca). (V) Structure of the repeating disaccharide (iduronic acid-glucosamine) unit of heparin; (b) A portion of 2D NOESY spectra of heparin (I), heparin–Mg²⁺ (II), and heparin–Ca²⁺ (III) in 99.95% D₂O at 37 °C. Assignments are shown for the characteristic NOE cross-peaks. (IV) Bar plot representation of intra- and inter-residue NOE cross peak volumes. (V) Change in NOESY cross peak intensities of inter-residue A1-I4 and A1-I3 protons of heparin (blue), heparin–Mg²⁺ (cyan), and heparin–Ca²⁺ (orange).