Verification of Exposure to Cholinesterase Inhibitors: Generic Detection of OPCW Schedule 1 Nerve Agent Adducts to Human Butyrylcholinesterase

Abstract

Phosphylated butyrylcholinesterase is one of the most important biomarkers to verify an exposure to nerve agents, and it can be analyzed with liquid chromatography-tandem mass spectrometry (LC-MS-MS) by detection of a phosphylated nonapeptide that results after digestion of butyrylcholinesterase (BuChE) with pepsin. For a sensitive analysis (low degree of BuChE inhibition), the identity of the cholinesterase inhibitor has to be known in order to use the LC-MS-MS instrument in the most sensitive selected reaction monitoring mode. In practice, the identity of the cholinesterase inhibitor will not be known beforehand, and the number of possible organophosphates is greater than 1000. However, the number of possible molecular masses of organophosphates is approximately 170. A method for which only 34 transitions in the multiple reaction monitoring mode have to be acquired in order to screen for an exposure to all Organization for the Prohibition of Chemical Weapons Schedule 1 nerve agents was developed.

Laboratory Analysis of Chemical Warfare Agents, Adducts, and Metabolites in Biomedical Samples

“…There are several strategies available to verify exposure to nerve agents. It is not feasible to measure the intact reagent, because the half-life of these agents is only a few hours, which means that they disappear within 1 day after exposure (Benschop and de Jong, 2001;van der Schans et al, 2008a). Metabolites, often alkyl-methylphosphonic acids, are better biomarkers because they circulate for a longer period of time and are gradually excreted in urine (Shih et al, 1994;Fredriksson et al, 1995;Nagao et al, 1997;Noort et al, 1998).…”

“…The number of different OPs exceeds several thousand, but the number of different masses is only 170. Because the OPCW Schedule 1 nerve agents consist only of saturated alkyl groups with mass increments of 14 units, the number of mass possibilities can be further reduced to 36 masses, which means that only 36 multiple reaction monitoring (MRM) transitions have to be recorded (van der Schans et al, 2008a). It is anticipated that the newest mass spectrometers will be able to acquire all MRM transitions, relevant to all nerve agents.…”

Mass Spectrometric Identification of Chemical Warfare Agent Adducts with Biological Macromolecule for Verification of Their Exposure

“…Other BuChE-Organization for the Prohibition of Chemical Weapons (OPCW) Schedule 1 nerve gas adducts have also been analyzed. 19) Recently, tandem MS with a capillary LC and electrospray ionization (ESI) ion source or postsource decay MALDI-TOF MS has been used widely for peptide sequencing of protein digests in proteome research. 20) Identification of the protein is possible by the integration of sequence information on the obtained peptide segments.…”

Development and validation of a sensitive gas chromatography–ammonia chemical ionization mass spectrometry method for the determination of tabun enantiomers in hemolysed blood and plasma of different species

“…This technique allows a retrospective detection after several weeks. Recently, LC-MS assays have been introduced which target tabun adducted to peptides after enzymatic cleavage of tabun-phosphylated butyrylcholinesterase [7] or albumin [8], prolonging the possible retrospective detection to several months. Although all these methods are valuable in the verification analysis of tabun exposure, they cannot be applied to the intended toxicokinetic and toxicodynamic studies, as they do not yield information of the original amounts of (+)-and (−)-tabun.…”