Advances in the mass spectrometry of hemoglobin adducts: global analysis of the covalent binding of butadiene monoxide

A common method to assess exposure to 1,3-butadiene through both occupation al and environmental routes involves the detection of hemoglobin adducts fo rmed by the primary reactive metabolite butadiene monoxide (EB). This assay is a modification of the Edman degradation procedure, which was developed to determine adducts formed specifically at the amine group of the N-termin al valine of hemoglobin. The goals of the current research are to determine the global modification of alpha- and beta -globin chains by EB and to loc alize the primary reactive residues to specific regions of the globin polyp eptides. The degree of modification was monitored by electrospray mass spec trometry, which was used to measure the formation of EB-hemoglobin adducts (up to ten adducts per globin). Structural analysis of these modifications was performed by peptide mapping of globin peptides after trypsin digestion using liquid chromatography-mass spectrometry. These experiments provided information as to the relative reactivity of alpha- and beta -globin toward s EB, as well as to the localization of adducts to specific peptide sequenc es. The results reveal variable reactivities of alpha- and beta -globin tow ards EB and also show the formation of multiple adducts at several alpha- a nd beta -globin sites. In addition, it is established that the N-terminal v aline residues are not the first to be modified by EB. (C) 2001 Elsevier Sc ience Ireland Ltd. All rights reserved.