Structural basis for the biological effects of Pr(III) ions: alteration of cell membrane permeability.

The biological effects of rare-earth ions on the organism have been studied using Pr3+ as a probe ion and Escherichia coli cell as a target. Atomic force microscopy (AFM) observation of the surface of E. coli cells shows that the presence of Pr3+ substantially changes the structure of the outer membrane. By induced coupled plasma-mass spectrometry (ICP-MS), more Cu2+ was found in the cells grown in the presence of Pr3+, indicating changes of cell permeability. Using energy dispersive X-ray spectroscopy (EDX), Ca2+ is found on the outer surface of the original cell. It is proposed that Pr3+ can replace Ca2+ from the binding sites because of their close ionic radii and similar ligand speciality.