Principles of selective inactivation of viral genome. II. Influence of stirring and optical density of the layer to be irradiated upon UV-induced inactivation of viruses.

Kinetics of the UV-induced (lambda = 254 nm) inactivation of phage MS2 is studied for stirred and non-stirred solutions with optical densities ranging from 0.06 to 2.1. The extent of inactivation exhibits exponential dependence on irradiation time for stirred solutions thus indicating the homogeneity of the phage population in respect to photosensitivity of infectivity. Irradiation of the same solution without stirring results in deviation of survival curves from exponential ones (the so called "tailing"), being more pronounced the larger the optical density of the layer under irradiation and degree of inactivation. Such a deviation is conditioned by non-uniform light absorption by virions in solution in the absence of stirring. The inactivation kinetics upon UV-irradiation of the stirred and non-stirred phage solutions is rather accurately expressed by respective equations thus enabling the choice of rational conditions for a given depth of phage inactivation to be performed.