Abstract
We studied the protective effect of ascorbic acid against DNA double-strand breaks (DSBs) caused by photo-induced reactive oxygen species under crowding environments using the observation method of a single DNA molecule with fluorescence microscopy. The protective effect of ascorbic acid against DSBs under different crowding conditions was evaluated by measuring the first double-strand breaNage time of individual DNA molecule from the start of the focusing of visible light to each DNA molecule. The solution containing different concentrations of polyethylene glycol (PEG, molecular weight: 6000) was prepared as a model solution of crowding environments. This solution was used for the experiment of DSBs. As a result, ascorbic acid and PEG exerted an additive protective effect against DSBs under crowding environments. Such an additive protective effect against DSBs could provide an important suggestion on the actual protective effect of ascorbic acid in living cellular systems, where the intracellular medium is highly crowded with biomacromolecules.
