Photodynamic Action of Proflavine on Coliphage T3 I. Kinetics of Inactivation

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The photodynamic inactivation of coliphage T3 was studied over a wide range of concentrations of the dye proflavine. With 2 × 107 phage/ml, two modes of inactivation were observed. Between 0.25 and 12 to 13 μg/ml, inactivation was biphasic. There was an initial first-order inactivation (R×1) which became temporally associated with an apparently multiorder process (R×2) at higher light doses. Dye concentrations above 12 to 13 μg/ml showed only two-target inactivation curves (R×3), except at high dye concentrations where processes kinetically identical to R×1 and R×2 reappeared. R×2 showed a normal rectangular hyperbolic saturation curve but R×1 and R×3 appeared to saturate prematurely. The saturation behavior of R×1 and R×2 was independent of phage concentration, but R×3 was lost at phage titers above 2 × 107/ml. No dark inactivation was seen with R×1 and R×2 subsequent to a period of illumination. With R×3, an exponential dark inactivation was seen for at least 1 hr after a period of illumination. The dye-phage system equilibrated immediately, at any temperature, at proflavine concentrations where R×1 and R×2 occurred. With R×3, prolonged equilibration times were necessary. Moreover, there was a temperature effect. The rate of inactivation at equilibrium was temperature-dependent, whereas the initial rate at which equilibrium was approached was essentially temperature-independent.

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