Interaction of Amino Acids with Transition Metal Ions in Solution (I) Solution Structure of L-Lysine With Co (II) and Cu (II) Ions as Studied by Nuclear Magnetic Resonance Spectroscopy

Abstract

Interaction of L-lysine with Co(II) and Cu(II) ions has been studied using ¹H- and ₁₃C- NMR and solution absorption spectrometry. In L-lysine-Co²⁺ solution in D₂O (100:1 in concentration), coordination interaction of the α-amino and carboxyl groups with Co²⁺ occurs from the neutral to alkaline pD region, whereas no interaction of the ε-amino group was observed throughout the whole pD region. On the other hand, in L-lysine-Cu²⁺ solu-tion, the ε-amino group also takes part in complexation in the higher pD region (pD_??_10). Structural changes in complexation of L-lysine with the divalent cations along with pD variations in aqueous solution are discussed. Dissociation constants of the three functional groups were obtained by ¹H-NMR chemical shifts; pKa₁=2.2, pKa₂=9.5 and pKa₃=11.2.