Electroendosmosis in Agarose Gel Electrophoresis

  • In agarose gel electrophoresis, electroendosmosis (EEO) can be defined as ‘the active water transport towards cathode (negative electrode) from anode (positive electrode) through the agarose matrix under the influence of electric field due to immobilized negatively charged groups (sulfate and carboxyl) on agarose matrix.
  • Groups like carboxyl and sulfate become ionized in basic and neutral agarose gel electrophoresis buffers (e.g., TAE or TBE, pH 8.0). Under the electric field, these negative charged groups are attracted by the anode. Since they are affixed, they do not move, however, their counter ions (H3O+) move towards the cathode. It causes smearing and blurred zones of nucleic acid, and drying of agarose gel in the anodal area due to internal convection.
  • EEO flow was first reported in clay plugs by F.F. Reuss (1809). EEO flow is caused by the Coulomb force induced by an electric field.
  • EEO is a potentially significant problem in low quality agarose, which has high sulfate content. The use of ultrapure agarose with low sulfate and carboxylate content can greatly reduce this problem.

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