Agarose gel electrophoresis of bacteriophages and related particles

Viruses and related particles have been fractionated by electrophoresis through gels. For agarose gels, the radius at the exclusion limit for spheres varies from 1500 nm in a 0.04% gel to 3.6 nm in a 4.0% gel. Thus, the size of the gel's pores can be adjusted to sieve all known viruses. By measurement of electrophoretic mobility (μ) as a function of agarose concentration, the μ in the absence of a solid support (μ₀) can be determined for any particle. From the shape of a semilogarithmic plot of μ as a function of agarose percentage, a rod-shaped particle can be discriminated from a spherical particle. The sphere's radius can be determined from this plot with an accuracy of ±8%. Accuracy of ±1% has been more recently achieved using two-dimensional agarose gel electrophoresis. Though bacteriophages have been the primary object of study, the above techniques of agarose gel electrophoresis have also been applied to plant viruses and should be applicable to animal viruses. The μ₀ values measured for bacteriophages with and without their tail fibers suggest a mechanism of controlling attachment to a host. A related mechanism is proposed for the control of the virulence of animal viruses. Measurement of outer radius for different forms of the capsid of bacteriophage P22 reveals variability in outer radius too small to be detected by electron microscopy.