Fig. 3: Reversible disulfide interstrand crosslinking in 2′-deoxythioguanosine (TG)–containing DNA duplexes.

a Schematic representation of the reversible disulfide interstrand crosslinking reaction in TG-containing DNA duplex. Crosslinking is induced under oxidative conditions (either chemically using I₂ or via photoirradiation with 365 nm UV light) and reversed under reducing conditions using DTT. PAGE analysis of disulfide crosslinking via chemical oxidation. b ODN strands (10 µM each) were prepared in phosphate buffer (pH 7.0, 20 mM) containing NaCl (100 mM) and incubated with oxidizing agent, I₂ (100 µM) at 10 °C for 1.0 h (−DTT condition). c ODN duplexes were treated with DTT at a 2:1 (200 µM DTT: 100 µM I₂) or 1:2 ratio (+DTT condition). PAGE analysis of photoinduced crosslinking. d ODN strands (10 µM each) were prepared in phosphate buffer (pH 7.0, 20 mM) containing NaCl (100 mM) and photoirradiated with 365 nm LED light (UV light intensity: 3.0 W/m²) for 10 s and 30 s at 0 °C (−DTT condition). e Duplex photoirradiated for 30 s with DTT (200 µM) or incubated with DTT (200 µM) after 30 s of irradiation (365 nm LED light, intensity: 3.0 W/m²) (+DTT condition). PAGE analysis condition: 16% acrylamide, 20% formamide, and SYBR^TM Gold staining.