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Identification of Covalent Binding Sites of Phthalic Anhydride in Human Hemoglobin

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journal contribution
posted on 17.11.2008, 00:00 by Marina C. Jeppsson, Bo A. G. Jönsson, Monica Kristiansson, Christian H. Lindh
Phthalic anhydride (PA) is a reactive low molecular weight compound used in the chemical industry. The exposure of PA may lead to work-related airway diseases such as rhinitis, chronic bronchitis, and asthma. The exposure gives rise to an increase in hapten-specific IgG antibodies in workers but with a low presence of specific IgE antibodies. In this study, the binding of PA to human hemoglobin (Hb) in vitro was investigated. Trypsin and Pronase E digestion, LC, LC/MS/MS, GC/MS analysis, and nanoelectrospray hybrid quadrupole time-of-flight MS were used to identify the adducted amino acids of the synthesized PA-Hb conjugates. In the conjugate with the molar ratio 1:0.1, a total of six adducted amino acids were identified. N-Terminal valine was found adducted in both the α- and the β-chains as well as a total of four lysines, Val 1, Lys 16, and Lys 61 on the α-chain and Val 1, Lys 66, and Lys 144 on the β-chain. Two types of lysine adducts were found, a phthalamide and a phthalimide. It was also found that PA differs in its binding site as compared to hexahydrophthalic anhydride. The result of this study suggests several interesting applications of biological monitoring.