Description:
<jats:title>Abstract</jats:title><jats:p>Transient electric birefringence measurements of the bacteriophages T2L0 and T6 were performed under such conditions that the tail fibers are extended. The data obtained are compared to previously reported data for T4B. For all T‐even phages the degree of extension of the tail fibers is a function of pH, ionic strength, and temperature. For T4B, much higher ionic strengths are needed than for T2L0 and T6 to accomplish complete tail‐fiber extension. The rotational diffusion coefficients of the phages with fully extended fibers are equal to 120 ± 3 sec<jats:sup>−1</jats:sup>, 132 ± 5 sec<jats:sup>−1</jats:sup>, 157 ± 4 sec<jats:sup>−1</jats:sup> for T2L0, T4B, and T6, respectively. The respective optical anistropies are − (2.66 ± 0.05) × 10<jats:sup>−4</jats:sup>, and − (3.07 ± 0.15) × 10<jats:sup>−4</jats:sup>. The differences in the rotational diffusion coefficient and optical anisotropy arise because the conformation of the fully extended tail fibers is different for the three phages. The tail fibers of T2L0 project further into the solution (away from the head) than do those of T4B and T6. The apparent permanent dipole moments of T2L0 and T6 decrease with increasing ionic strength. This decrease is caused by the screening of the surface charges on the phage body by the counter‐ions in the solution. The biological relevance of this decrease is illustrated by the fact that the adsorption rate of T6 phages to <jats:italic>E. coli</jats:italic> B bacteria shows a similar dependence of ionic strength. Evidence is pressented that the tail fibers may move more or less independently of the phage body when an electric field is applied to the suspension.</jats:p>