Mass spectral characterization of tabun-labeled lysine biomarkers in albumin

•Tabun-labeled lysine peptides were found in three kinds of albumin exposure to tabun in vitro.•Tabun-labeled lysine peptides were identified in rabbit albumin in vivo in 24 h.•Characteristic ions of tabun-labeled lysine adducts were found in the MS/MS spectra.•Structural characteristic calculations and molecular docking were employed to study the structure characteristics and potential molecular binding affinity of tabun-labeled lysine.

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.