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

Abstract

Exposure to chemical warfare agents (CWAs) can be verified by detecting their degradation products in biological samples. However, the half-lives of these CWA degradation products in the body are short. CWAs are known to combine with biological macromolecules and the covalently bound compounds are called adducts. The residence time of adducts in the human body is longer than that of the corresponding CWA degradation products. Therefore, development of analytical methods to detect these adducts is a more realistic way of verifying CWA exposure. In this mini review, we describe the present state of research on analytical methods for identifying CWA adducts, and mainly introduce our research on nerve gas adducts using a direct method. Novel analytical methods for verifying low level exposure to nerve gases use liquid chromatography-mass spectrometry (LC-MS). Butyrylcholinesterase (BuChE) has been purified by affinity chromatography and sodium dodecylsulfate poly-acrylamide gel electrophoresis. The purified enzyme is inhibited by nerve gases (sarin, VX and soman) and digested by chymotrypsin, and then the peptides are analyzed by LC-MS and LC tandem MS. The peptide fragment that is combined with nerve gas is detected by LC-MS. Furthermore, the chemical structure of the adduct peptide characterized by MS provides structural information about the analyte. The detection limit of BuChE or BuChE adduct is estimated at 4 ng/injection (53 fmol/injection). If at least 1% of BuChE activity is inhibited by nerve gas, the adduct can be detected at a level of 1% BuChE inhibition in the victim's serum.