Study of the radiosensitive structure of T2 bacteriophage using low energy electron beams.

Hydrated T2 bacteriophage were irradiated with 0.75 to 90 kev electron beams. A thin foil isolated the sample chamber from the electron gun source. Survival (plaque formation) was observed. Apparent cross-sections and D(37) doses were determined. The maximum cross-section of about 5 x 10(-3) mu(2) is roughly equal to the cross-sectional area presented by the phage core. As beam energy was increased the average D(37) dose first attained a minimum value of about 23 kr for 1 kev electrons (which penetrate the relatively inert protein coat) after which the average D(37) dose rose with beam energy to a maximum value of about 50 kr for fully penetrating beams. These dependencies suggest that the radiosensitive structure exists as a peripheral shell rather than a uniformly sensitive core. A tentative model for the phage structure, based on this and other evidence, is presented.