The aim of the proposed research is to develop a ligand to selectively complex 82Rb+ in the presence of excesses of Na+ and K+, for use in positron emission tomography (PET). A particular technological innovation would be to use 82Rb complexes in place of 15O for brain scanning. 82b+ is conveniently obtained from an 82Sr generator, unlike 15O, which is obtained from a cyclotron, limiting use of PET. A review of present knowledge shows that no ligands except calixarenes and calixacrowns show significant selectivity for Rb+ over Na+ and K+. Molecular mechanics (MM) calculations are used to analyze the factors that enhance selectivity for Rb+ over Na+ and K+. Strategies based on MM are outlined for synthesizing unique complexing ligands that will have high Rb+/Na+ selectivity. If successful, the project would provide a thermodynamically and kinetically stable metal ligand complex capable of crossing the blood brain barrier.
