Comparative study of kinetics on DNA double-strand break induced by photo- and gamma-irradiation: Protective effect of water-soluble flavonoids

► We performed the kinetic study on the fragmentation of giant DNA caused by visible light and γ-ray irradiation using fluorescence microscopy. ► The protective effect of two different water-soluble flavonoid derivatives was compared in a quantitative manner. ► Marked difference on the relative protective ability of these compounds was found depending on the source of irradiation, either visible light or γ-rays.