XWH - 06 - 1 - 0102 TITLE : Neurotoxin Mitigation PRINCIPAL INVESTIGATOR :

Our goal was to determine whether chlorpyrifos oxon, dichlorvos, diisopropylXuorophosphate (DFP), and sarin covalently bind tohuman albumin. Human albumin or plasma was treated with organophosphorus (OP) agent at alkaline pH, digested with pepsin at pH2.3, and analyzed by matrix-assisted laser desorption/ionization time-of-Xight (MALDI-TOF) mass spectrometry. Two singly chargedpeaks m/z 1718 and 1831, corresponding to the unlabeled peptide fragments containing the active site Tyr411 residue, were detected in allsamples. The sequences of the two peptides were VRYTKKVPQVSTPTL and LVRYTKKVPQVSTPTL. The peptide–OP adducts ofthese peptides were also found. They had masses of 1854 and 1967 for chlorpyrifos oxon, 1825 and 1938 for dichlorvos, 1881 and 1994 forDFP, and 1838 and 1938 for sarin; these masses Wt a mechanism whereby OP bound covalently to Tyr411. The binding of DFP to Tyr411of human albumin was conWrmed by electrospray tandem mass spectrometry and analysis of product ions. None of the OP–albuminadducts lost an alkoxy group, leading to the conclusion that aging did not occur. Our results show that OP pesticides and nerve agentsbind covalently to human albumin at Tyr411. The presence of Tyr411 on an exposed surface of albumin suggests that an antibodyresponse could be generated against OP–albumin adducts.© 2006 Elsevier Inc. All rights reserved.