Agarose gel pore radii are not dependent on the casting buffer.

Previous studies have shown that the apparent pore size of agarose gels is dependent on the buffer in which the gel is cast and run (D.L. Holmes and N.C. Stellwagen, Electrophoresis 1990, 11, 5-15; N.C. Stellwagen and D.L. Holmes, Electrophoresis 1990, 11, 649-652). However, these studies, based on the mobility of DNA restriction fragments, neglected the effect of electroendosmosis. By measuring the mobility of vitamin B12 under various experimental conditions, it is shown here that electroendosmosis is highly buffer-dependent. When the observed mobilities of DNA are corrected for electroendomosis, the apparent pore radii of agarose gels are found to be independent of the casting buffer.