The Indirect Action of γ-rays on the Coat Protein of Bacteriophage Particles

SummarySuspensions of bacteriophage T4 in 25 mM phosphate buffer, pH 7·1, were irradiated with 60Co γ-rays. Measurements of the viscosity of irradiated samples before and after treatment with DNA-ase and trypsin showed that DNA is released from damaged phage particles. The phage debris acts as an effective radical scavenger and at higher doses protects the residual phage, thereby decreasing the inactivation rate. In irradiated suspensions of T4 and ΦX174 phage particles biologically-active subviral particles able to infect bacterial spheroplasts were found. Sedimentation in a sucrose gradient showed that the subviral particles of T4 have nearly the same sedimentation coefficient as unirradiated particles. Examination of irradiated samples with the electron microscope revealed that they contained many particles with the sheath contracted. The subviral particles produced by irradiation resemble those obtained with urea but do not show the tail clusters found in samples treated with urea.