2 deoxyguanosine dg

N-acetylcysteine, calf thymus DNA (sodium salt, Type I), nuclease P1, micrococcal nuclease, spleen phosphodiesterase, NADPH, 2′-deoxyguanosine (dG), and 2′-deoxyadenosine (dA) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Dimethylformamide, acetonitrile, potassium carbonate, chloroform, diethyl ether, and phosphate buffered saline were obtained from Fisher Scientific (Pittsburg, PA, USA). AX 1-X8 anion exchange resin was purchased from Bio-Rad (Hercules, CA, USA). All solvents used were high performance liquid chromatography (HPLC) grade.
Dehydromonocrotaline was synthesized by dehydrogenation of monocrotaline in chloroform with o-chloranil, as previously described [19 (link)]. DHP was obtained from the metabolism of riddelliine by rat liver microsomes [27 ]. DHP-dG-1, DHP-dG-2, DHP-dG-3, DHP-dG-4, DHP-dA-1, DHP-dA-2, DHP-dA-3, and DHP-dA-4 adducts were synthesized as previously described [10 (link),19 (link)]. Isotopically labeled DHP-[¹⁵N₅]dG and DHP-[¹⁵N₅, ¹³C₁₀] dA adducts, used as internal standards for quantitation of DHP-dG and DHP-dA adducts by liquid chromatographytandem mass spectrometry (LC/MS/MS), were synthesized as described previously [8 (link),10 (link)].
Male human liver microsomes and male Fischer 344 rat liver microsomes were purchased from Bioreclamation IVT (Baltimore, MD, USA). DNA concentrations were determined spectrophotometrically.