Affinity capillary electrophoresis (ACE) provides a new approach to studying protein-ligand interactions. The basis for ACE is the change in the electrophoretic mobility of the protein when it forms a complex with its ligand. This binding interaction can be quantified directly for charged ligands or indirectly for neutral ligands in competition with a previously characterized charged ligand. Determination of kinetic and equilibrium constants using ACE relies only on the changes in the migration time and shape (but not the area) of the peak due to protein. Simulation of the protein mobility under conditions of ACE suggests that the experimentally obtained electropherograms can be explained in terms of few variables: on and off rates (and thus, binding constant), concentration of the ligand(s), and relative mobilities of the protein and its complex(es).

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Chiral dirhodium(II) tetrakis[methyl 2-oxypyrrolidine-5(S)-carboxylate] has been immobilized on polystyrene-poly(ethylene glycol) and Merrifield resins.Intra-and intermolecular cyclopropanation reactions with these catalysts demonstrate their high selectivity, comparable to or better than their homogeneous counterpart, and recovery and reuse for up to nine sequential applications have been achieved without loss of selectivity. Catalyst stability is related to the percentage of available sites to which the ligand is affixed, but the percentage of ligand sites on the polymer that are bound to dirhodium(II) does not appear to influence stability or selectivity.