Increased Yields of the Guanine Oxidative Damage Product Imidazolone Following Exposure to LED Light

Among the bases of DNA, guanine is the most easily oxidized. Imidazolone (Iz) is a guanine oxidative damage, and we sought to generate Iz-containing oligomers. In this paper, we describe the methods and conditions to increase the yield of Iz by employing photooxidation reactions using light-emitting diodes (LEDs) with emission wavelengths of 365 nm and 450 nm. For photooxidation performed with the 450 nm LED source at light intensities of 2.75–275 mW/cm2, peak yields of Iz were 35% at light intensities of 27.5 and 68.8 mW/cm2. For reactions performed with the 365 nm LED source at light intensities of 5.12–512 mW/cm2, the peak yield of Iz was 34% at a light intensity of 51.2 mW/cm2. By varying the irradiation time, the maximum yield of Iz (34–35%) was obtained with irradiation times of 5–20 min using the 450 nm LED source at an intensity of 13.8 mW/cm2. Using the 365 nm LED source at an intensity of 25.6 mW/cm2, the maximum Iz yield obtained was 31% at irradiation times of 2–5 min. Thus, we obtained conditions that can provide an Iz yield of up to 35%.