Overlay independent X-ray data analysis for enhanced oxime OP-ChE reactivation

University Of California, San Diego, La Jolla CA

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Abstract

Overlay independent X-ray data analysis for enhanced oxime OP-ChE reactivation Project Summary. Vulnerability of large civilian and military populations to organophosphate (OP) exposure remains an unfortunate peril of the present day. Both, nerve agent OPs and OP based pesticides are realistic and alarmingly significant hazards. Recent horrifying massive nerve agent poisoning episodes in Syria and daily worldwide fatalities associated with OP based pesticide exposures reveal general lack of appropriateness of currently employed measures for counteracting OP intoxications. The emphasis is on affordability, availability and efficacy. More than two hundred AChE and BChE structures deposited in PDB in the past 25 years reveal unusually consistent protein conformations, not only of protein backbones but also of majority of amino acid side chains. This apparent absence of conformational flexibility registered at the low temperature and in the solid crystaline state, appears as a contrast to an extreemely high catalytic output, in particular in the long and narrow AChE active center gorge. Catalytically essential, thermally driven, ?breathing? fluctuations of the AChE and BChE protein backbones have long been suspected and proposed but have never been clearly demonstrated experimentally. In particular for oxime reactivation reactions backbone fluctuations appear essential due to highly restricted access to covalently attached OPs in the narrow actice center space impacted further by covalently bound OP conjugates. For design of an accelerated, efficient reactivator molecule it is critical to know what parts of active center have structural predisposition to move and facilitate nucleophilic oxime approach to the phosphorus atom in geometrically optimal fashion. This information is encripted in hundreds of resolved and deposited ChE structures and our goal is to extract it to an useful form. We expect to detect structural fluctuations small in magnitude yet systematic in nature. Our initial manual analyses confirm those expectations.