8 hydroxy 2 deoxyguanosine 15n5

Both 8-hydroxy-2′–deoxyguanosine (purity ≥ 98%) and 5-hydroxymethyluracil (purity 97%) were purchased from Sigma-Aldrich (St. Louis, MO, USA), and 8-hydroxy-2′-deoxyguanosine-15N5 (purity 95%) was purchased from Cambridge Isotope Laboratories, Inc. (Tewksbury, MA, USA). 8-hydroxyguanosine (purity ≥ 98%), 8-isoprostane (purity ≥ 99%), and 8-isoprostane-d4 (purity ≥ 99%) were obtained from Cayman Chemical (Ann Arbor, MI, USA). 8-hydroxyguanosine-13C,15N2 (purity 98%), 4-hydroxynonenal (purity ≥ 98%), and 4-hydroxynonenal-d3 (purity 97%) were purchased from Santa Cruz Biotechnology (Dallas, TX, USA). Methanol (LC-MS grade) was purchased from Burdick and Jackson (Muskegon, MI, USA). Formic acid and ammonium hydroxide were obtained from Sigma-Aldrich (St. Louis, MO, USA). Strata-X-A cartridges (33 µm Polymeric Strong Anion, 200 mg/3 mL; 8B-S123-FBJ), analytical columns (Kinetex phenyl-hexyl column, 100 mm × 4.6 mm, 2.6 µm particle size; 00D-4495-E0), and Kinetex C18 column, (100 mm × 4.6 mm, 2.6 μm particle size, 00D-4462-E0) were purchased from Phenomenex (Torrance, CA, USA).

Calf thymus DNA-sodium salt (ct-DNA), potassium phosphate monobasic and potassium phosphate dibasic were purchased from Sigma-Aldrich Corp (St. Louis, MO, USA). 4,6-Diamino-5-formamidopyrimidine-¹³C,¹⁵N₂ (Fapy adenine-¹³C,¹⁵N₂), 2,6-diamino-4-hydroxy-5-formamidopyrimidine-¹³C,¹⁵N₂ (Fapy guanine-¹³C,¹⁵N₂), 8-hydroxyadenine-¹⁵N₅ (8-OH-adenine-¹³C,¹⁵N₂), 5-hydroxy-5-methylhydantoin-¹³C,¹⁵N₂ (5-OH-5-MeHyd-¹³C,¹⁵N₂) and 8-hydroxy-2′-deoxyguanosine-¹⁵N₅ were purchased from Cambridge Isotope Laboratories (Andover, MA). 8-Hydroxyguanine-¹⁵N₅ (8-OH-guanine-¹⁵N₅) was obtained by hydrolysis of 8-hydroxy-2′-deoxyguanosine-¹⁵N₅ with 60% formic acid at 140°C for 30 min followed by lyophilizing. Subsequently, 8-OH-guanine-¹⁵N₅ was dissolved in 10 mmol/L NaOH before use. E. coli formamidopyrimdine DNA glycosylase (Fpg) and E. coli endonuclease (III) (EndoIII) were purchased from Trevigen (Gaithersburg, MD).