Radiation-induced generation of chlorine derivatives in N₂O-saturated phosphate buffered saline: Toxic effects on Escherichia coli cells

The radiolysis of aqueous chloride solutions has been investigated using pulse and steady-state methods. We have found a correlation between the yields of Cl₂^- and HOCl formed in pulse-irradiated N₂O-saturated solutions. The yields increased with the increasing concentrations of Cl^- and phosphate. Phosphate enhanced the yield of Cl₂^- in neutral solutions because of a proton transfer from H₂PO₄^t̄ to HOCl^- with a rate constant of (2.6 ± 0.5) × 10⁸M^-1s^-2. HOCl could not be detected in pulse-irradiated He or air-saturated, phosphate-buffered saline (PBS) solutions or in gamma-irradiated N₂O, He, or air-saturated PBS solutions. The results are discussed in light of previously suggested mechanisms for the formation and decay of Cl₂^-. Pulse-irradiated N₂O-saturated PBS solutions have a lethal effect on Escherichia coli cells, which is proportional to the amount of HOCl in the solutions. Gamma-irradiation of cells in N₂O-saturated PBS solution also raises the radiosensitivity of the cells, although HOCl does not accumulate in this system. The effects of the radiation-induced toxic products on E. coli cells are similar to the effects of NaOCl. The cell membrane is probably the site of physiological injury induced by the radiation products.