Analysis of convex Ferguson plots in agarose gel electrophoresis by empirical computer modeling

Agarose gel electrophoresis has been shown to give rise to non‐linear plots of log (mobility) vs. gel concentration of spherical viruses (Serwer,[1]) and cellular vesicles (Gottlieb et al. [2]). This finding also applies to proteins as shown in this study. Considering that in the non‐linear plot, the slope becomes a function of gel concentration, it is possible to determine particle properties and gel parameters by a modification of the conventional method derived from the Ogston theory for long‐fiber gels. This treatment shows: (a) In application to data obtained from gel electrophoresis (0.4 to 1.6 % agarose) of viruses (13 to 42 nm radius) and with increasing gel concentration: (i) an increase of apparent total fiber length per g agarose matrix, (ii) a reduction of apparent fiber radius and (iii) a constant fiber volume (per g matrix material) of the agarose fiber. The values of the fiber radii identify the fibers as agarose supercoils (or aggregates of it) with a radius of 20–55 nm. (b) In application to data obtained from gel electrophoresis (1.2 to 8 % agarose) of proteins (1.7 to 5.8 nm radius): a fiber volume indicative of additional sieving by the agarose double helix (of known radius of 0.5–2 nm). This is in agreement with a previous suggestion by Serwer [1] that proteins are able to penetrate into the double‐helical network of which the agarose supercoil consists. (c) The likelihood of a continuous transition from case (a) to case (b).