<prompt> The most widely used method for determining the purity of a protein is?Isoelectric focusingPolyacrylamide gel electrophoresisIon exchange chromatographyHigh pressure chromatography  <response>: The most widely used method for determining the purity of a protein is polyacrylamide gel electrophoresis PAGE in the presence of an anionic detergent, sodium dodecyl sulphate SDS. Electrophoresis separates the charged biomolecules based on the rates at which they migrate in an electrical field. Reference: Harpers illustrated biochemistry 30th edition 