Radiosensitization of Serratia marcescens by nitropyridinium compounds.

The two nitropyridinium compounds tested sensitize hypoxic Serratia marcescens to irradiation up to the oxygen enhancement level by two components which can be separated as a function of compound concentration. Sensitization above the initial plateau level is in order of their determined one-electron reduction potentials, Ro 03-5580 (E 7 1 = -335 mV) being more efficient than Ro 03-5637 (E 7 1 = -358 mV). Additivity in sensitization up to a maximum enhancement level of 2.1 +/- 0.1 is found on combining these hydrophilic compounds at concentrations to give sensitization at the plateau level, with the hydrophobic sensitizer paranitroacetophenone (PNAP). It is concluded that the nitropyridinium compounds and PNAP sensitize the same site.