Concentration effects of methylene blue (MB) and oxygen on the photoinactivation rate of Q \beta bacteriophage were examined. The effect of initial virus concentration was verified on the similar f2 phage. The inactivation rate, k, is an increasing function of MB and O 2 concentration and shows saturation with respect to MB concentration. Thus the results suggest that MB must adsorb to Q \beta sites and oxygen must be present for photoinactivation to occur. The inactivation rate is independent of the initial number of phage particles present before inactivation, indicating that inactivation does not depend upon interaction among viral particles or on surface effects. The results indicate that at least two different viral phenotypes exist within the wild-type Q \beta and f2 populations: one susceptible and the other resistant.
D. Lee, M. Foux, E. F. Leonard, "The Effects of Methylene Blue and Oxygen Concentration on the Photoinactivation of Q \beta Bacteriophage," Photochem Photobiol,65, 161 (97).