N-acetylaspartate complexes with calcium and lanthanide ions

N-acetylaspartate (NAA) is the one of the most prominent resonances observed in the solvent-suppressed NMR spectrum of the human brain. Although it is present in the brain at about 10 mM, its precise metabolic function is still unclear, We have examined the NAA as a potential chelator for divalent metal ions such as Ca²⁺. We have employed the perturbations induced by Ln³⁺ ions in the ¹H and ¹³C NMR spectrum of NAA to monitor formation of NAA complexes. ¹ NMR measurements showed that the dissociation constants for the formation of Eu³⁺-NAA, Yb³⁺-NAA, and Ca²⁺-NAA complexes were 0.07, 0.13, and 0.86 mM, respectively. Scatchard analysis of the results indicates the formation of a 1:1 metal-ligand complex. We also inferred the structure of the NAA-metal ion complex from a analysis of paramagnetic perturbations induced in the ¹H NMR and ¹³C NMR spectra of NAA. The structural analysis of the NAA-metal ion complex indicates that the two carboxylic groups participate in chelating the metal ion, forming the binding site for the metal ion.