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Action of Trypsin on Peptides

Predict the action of trypsin upon the following peptides. If the resulting fragments undergo electrophoresis at pH 7, will they migrate to the anode, cathode, or remain at the origin?
a. Lys-Asp-Gly-Ala-Ala-Glu-Ser-Gly
b. Ala-Ala-His-Arg-Glu-Lys-Phe-Ile
c. Tyr-Cys-Lys-Ala-Arg-Arg-Gly

Solution Preview

Trypsin is a serine protease produced by the pancreas that breaks apart peptide bonds at the carboxyl end of the amino acids lysine and arginine (except, if they are followed by proline). This will create fragments that have a charge based on whether their amino end (positive charge) is left open or carboxyl end is left open (negative charge)

Electrophoresis separates proteins based on size and charge. Smaller peptide fragments will move faster and farther. The fact that in this question, the pH is 7 simply means that no charge is being added to the fragments. Undergoing acid electrophoresis or base electrophoresis helps to mask charges and separate based on size alone. Sometimes other chemicals are used to mask charge. But, here, in this question, charge will be taken into account. Positive fragments will be attracted to the cathode (which is negatively charged), and the negative fragments will be ...

Solution Summary

Three peptides are used to find theaction of trypsin and how these fragments move during electrophoresis is identified.