Our proposed project is directed to improving prophylaxis and therapy for organophosphate nerve agent organophosphate exposure through the design of mutant human acetylcholinesterases (AChEs), novel oximes and related reactivating nucleophiles. This strategy of "oxime-assisted catalysis" modifies AChE such that, when placed in the circulation, the oxime and AChE become a catalytic, rather than a stoichiometric, scavenger of organophosphates. Proof of principle has already been established for hydrolysis of a series of organophosphates, and we will refine AChE mutations and oxime structure to enhance catalytic rates for hydrolysis and retention in plasma space. Since oxime therapy, 2-PAM and HI-6, also reactivates inhibited AChE at the target site and the therapeutic benefits of long term oxime therapy have become fully appreciated recently, we propose to design new reactivators based on contemporary knowledge of AChE structure to which we and other groups have contributed to over the past two decades. This approach considers impaction of the active center gorge and angle of access of the oxime as limiting constraints in the design strategy. Moreover, the UCSD and TSRI groups have applied a novel freeze-frame, click chemistry to the development of reactivating agents using AChE-phosphonate conjugates as the template for synthesis of the triazoles. In addition to oxime assisted catalysis in plasma, new oximes and other nucleophiles will be developed as novel reactivating agents at the target site. This chemistry also enjoys the advantage of combinatorial screening for medium to high throughput in the synthesis-screening paradigm. Nucleophiles and nucleophile AChE combinations will be optimized for enhancing therapeutic efficacy to the particular offending organophosphate. Hence, our approach will both augment catalytic scavenging of organophosphates in the circulation and enhance reactivation at the target tissues.