Mass spectral characterization of tabun-labeled lysine biomarkers in albumin

Tabun has been shown to form phosphylated adducts on tyrosine residues in albumin in vivo and in vitro. However, in this work, tabun-labeled lysine adducts were found in albumin. Three types of albumin were treated with overdose of tabun in vitro and 17 tabun-labeled lysine residues were found: K4, K12, K224, K377, and K524 in bovine albumin, K186, K188, K212, K329, K414, and K525 in leporine albumin, and K79, K186, K188, K212, K376, and K525 in rat albumin. To investigate the modification of tabun in vivo, three leporines were injected with 0.8×LD₅₀ dose of tabun. The results showed that the labeled lysine residues in vivo, were consistent with modified lysines in vitro. Structure characteristics and the binding mode of 6 tabun-labeled lysines of leporine albumin were further analyzed using theory simulation and molecular docking in Discovery Studio. For the first time, we show that tabun-labeled lysine peptides are found in vivo and in vitro. These modified lysine peptides are good biomarkers for exposure to tabun in albumin of leporine and rat.