Conformational study of L-lysine in aqueous solution by lanthanide shift probes

Conformation of L-lysine in aqueous solution was investigated by lanthanide shift probes (Dy, Ho, Er, Tm and Yb). Reilley's method was employed to separate the contact and dipolar components of the ¹³C paramagnetic shifts. This study reveals that Cα shift has the largest contact contribution while the other carbon shifts are dominated by the dipolar contribution. The average overall conformation of L-lysine in aqueous solution is extended with the molecular backbone in trans form. In the complex, lanthanide ion coordinates to the carboxyl group with Ln—O bond length 2.2 Å and the whole ligand is located outside the zero-dipolar shift cone of the lanthanide ion. The electronic spin density distribution on the ligand nuclei shows that the spin polarization is the predominant mechanism of the contact interaction for nuclei in close proximity to the bound lanthanide ion.