Agarose gel electrophoresis of bacteriophages and related particles. IV. An improved procedure for determining the size of spherical particles

Attempts have been made to improve the accuracy with which sieving during electrophoresis in gels can be used to determine the size of viruses and related particles. Using as samples spherical bacteriophages and related particles of known radius (13.3–41.9 nm), it was found that electrophoretic mobility (μ) was a linear function of agarose concentration (A) in a hydroxyethylated agarose (SeaPlaque, Marine Colloids) for 0.4 ⩽ A ⩽ 1.6. The value of A extrapolated to a μ of 0 (A₀) was a decreasing function of particle outer radius and was independent of the solid support‐free μ. Procedures for determining outer particle radius from values of A₀ have been developed. When used with internal standards, these procedures measure outer particle radius with an accuracy of ±4 %.