1. Radiation-Induced Strand Breaks in DNA: Chemical and Enzymatic Analysis of End Groups and Mechanistic Aspects
2. The chemistry of single-stranded 4′-DNA radicals: influence of the radical precursor on anaerobic and aerobic strand cleavage
3. DNA Synthesis Arrest at C4‘-Modified Deoxyribose Residues
4. A buffered aqueous solution (200 μL, 20 mM phosphate, pH = 7.0, 0.1 M NaCl) of 0.3−2 nmol of single- or double-stranded oligonucleotides and 3−150 nmol of glutathione diethyl ester (GSH) were deoxygenated by treatment with argon. The thermostated solution (20 °C) was irradiated for 3−20 min (Osram 500 W, 320 nm cutoff filter) in a 4 × 5 mm quartz cuvette and directly injected on an anion exchange HPLC column (Macherey-Nagel Nucleogen 60-7 DEAE, 125 × 4 mm; eluent A: 20 mM KH2PO4, 20% acetonitrile, pH 7.0; eluent B: 20 mM KH2PO4, 20% acetonitrile, pH 7.0, 1 M KCl; gradient: 0 min 90% A, 20 min 52% A, 25 min 30% A, 28 min 10%A; flow rate: 1 mL/min) or on a reversed phase HPLC column (Waters Symmetry C18, 5 μm, 150 × 3.9 mm; eluent A: 0.1 M triethylammonium acetate (TEAA); eluent B: acetonitrile; gradient: 6% B to 14% B in 30 min, flow rate: 1 mL/min; column temperature: 30 or 50 °C). The amounts of4−6were determined from the peak areas divided by the calculated extinction coefficient of the corresponding oligonucleotides. Their identities were confirmed by MALDI-TOF MS and by comparison with independently synthesized oligonucleotides. The competition constantskH/kEwere determined from the dependence of the product ratio ((5+6)/4) on the GSH concentration according to a pseudo-first-order kinetic treatment.