Draw the electrophoretic separation of Trp, Cys, and His at pH 6.0.

Electrophoresis can be defined as the migration and separation of charged particles (ions) under the application of electric field. The system consists of two electrodes of opposite charges that is, anode and cathode which are connected by the medium known as electrolyte. The isoelectric point is the pH of an aqueous solution of an amino acid at which the molecules on average have no net charge. In an acidic solution, amino acids exist as cation, thus the movement of amino acid will be towards cathode which is the negative electrode. Movement of amino acid will be towards anode in basic solution when amino acids exist as anion.

The movement of amino acids towards anode or cathode will depend on the overall charge the amino acid is carrying at pH 6.0. At pH 6.0, tryptophan which is having isoelectric point of 5.9 has a charge of zero and thus, will not migrate. Cysteine which has isoelectric point of 5.0 has a partial negative charge and will move towards the anode which is the positive terminal. Histidine which has isoelectric point of 7.6 has a partial positive charge and thus, will move towards the cathode which is the negative terminal. That’s how the separation of amino acids is done electrophoretically.

Electrophoretic separation of Trp, Cys, and His at pH 6.0