Figure 7.

Aluminum ion binding to sodium heparin was monitored through ²⁷Al NMR experiments. (a) 1D ²⁷Al NMR spectra of 100 mM Al₂(SO₄)₃ sample, in the absence or presence of sodium heparin. The major and minor peaks, respectively, corresponding to [Al(H₂O)₆]³⁺ and [Al(H₂O)₅SO₄]⁺ species, are shown. The addition of sodium heparin leads to slight displacement and broadening of the ²⁷Al signal. (b) Longitudinal spin-lattice (T₁) relaxation of ²⁷Al signals measured through standard inversion-recovery experiments. (c) Translational diffusion coefficient (D_tr) of Al³⁺ ions measured through pulse field gradient NMR diffusion experiments. Upon the addition of heparin, a small decrease in ²⁷Al T₁ relaxation time (b) and D_tr coefficient (c) is observed, indicating the partial binding of Al³⁺ ions to heparin.