Quantitative Analysis of Oxidative DNA Damage

Nuclease P1 from Penicillium citrinum, phosphodieasterase I and II, alkaline phosphatase from bovine intestinal mucosa, DNase I and DNase II, benzonase 99%, BHT, deferoxamine mesylate and pentostatin were purchased from Sigma-Aldrich (Steinheim, Germany). RNase T1 was from Thermo Fisher Scientific (Waltham, MA, USA) and RNase A from Roche Diagnostic GmbH, (Mannheim, Germany). The 3 kDa cut-off filters were obtained from Millipore (Bedford, OH, USA). Chemicals for the synthesis of oligonucleotides were purchased from Sigma Aldrich, Fluka and Link Technologies. CuCl₂, L-methionine, L-ascorbic acid and alkaline phosphatase were purchased from Sigma-Aldrich. Hydrogen peroxide (30%) and solvents (HPLC-grade) were purchased from Fisher Scientific. 2′-deoxyadenosine monohydrate and 2′-deoxyaguanosine were purchased from Berry & Associates Inc. (Dexter, USA). Isotopic labeled internal standards of 5′R-cdA, 5′S-cdA, 5′R-cdG, 5′S-cdG, 8-oxo-dG and 8-oxo-dA (see Supporting Information) were prepared according to the previously reported procedures [31 (link)]. Ultrapure water (18.3 MΩcm) distilled and deionized water (Milli-Q water) were purified by a Milli-Q system (Merck-Millipore, Bedford, OH, USA).