It has been found that the 24-membered hexamino macrocylic ligand [24]N6O2 forms complexes with ATP and affords of 103 rate enhancement of the hydrolysis of ATP at neutral pH. This proposal describes studies on the mechanism of the reaction. By the design of modified ligands the role of complex formation, electrostatic catalysis, nucleophilic catalysis, and general acid-general base catalysis in this hydrolytic reaction will be analyzed. Additional studies will concertrate on defining the structure of these complexes and the effect of the ternary complex of divalent metal.ATP.ligand on the hydrolysis of ATP. The results of these model studies would be useful in furthering our understanding of the mechanism of biological reactions that utilize ATP as a substrate.