Agarose gel electrophoresis of bacteriophages and related particles. III. Dependence of gel sieving on the agarose preparation

The sieving of different preparations of agarose has been measured during agarose gel electrophoresis, using as samples a spherical bacteriophage and two spherical bacteriophage‐related particles with radii between 13.3 and 41.9 nm. Semilogarithmic plots of electrophoretic mobility as a function of agarose perentage (A) were linear for A ⩽ 0.85, but became progressively nonlinear as A increased above 0.85. The regions of linearity in these plots were used to measure gel sieving and to determine an effective gel fibre radius. The sieving of the different preparations increased in the order HGT[P] < ME < Seaplaque (hydroxyethylated) Isogel (additive containing) < SeaPrep 15/45 (hydroxyethylated) (trade names of preparations from Marine Colloids). However, the effective gel fibre radius did not differ significantly from 25 nm among HGT[P], ME, SeaPlaque and SeaPrep 15/45 agarose; for Isogel, this radius was 20 nm. These data have been interpreted to indicate that the comparatively high sieving of SeaPlaque, SeaPrep 15/45, and to some extent Isogel agarose was caused by a comparatively low agarose mass per fibre volume and high total fibre length per gel volume. For at least some particles smaller than those used here, it is likely that migration through the gel fibres detected here occurs during agarose gel electrophoresis.