Final answer:
Gel electrophoresis (option b) , particularly SDS-PAGE, is the most suitable method to determine the relative purity of a protein as it separates proteins by size after denaturing them and applying a uniform negative charge, eliminating charge-based mobility differences.
Step-by-step explanation:
The most suitable technique to assess the relative purity of a protein in a sample prepared is gel electrophoresis, specifically polyacrylamide gel electrophoresis (PAGE). Proteins are separated by size using PAGE, which involves an electric field applied to proteins in a gel. The process of SDS-PAGE can further denature the proteins and apply a uniform negative charge, removing influences from the native protein charges, making size the sole factor for separation.
During SDS-PAGE, proteins are coated with SDS, a negatively charged detergent, which ensures they move toward the anode in the electric field. Proteins are separated based on size, with smaller proteins migrating faster and farther within the gel matrix. Following separation, proteins can be visualized using sensitive stains such as silver stain or Coomassie Brilliant Blue which highlights the position of each protein, providing an understanding of their relative abundances and purity.
In the context of assessing protein purity, other techniques like western blot analysis are useful for detecting specific proteins post-separation, thus contributing to qualitative rather than quantitative analyses of purity. Gel-filtration chromatography and ion-exchange chromatography are methods that can help to purify proteins but do not inherently provide information on the relative purity of proteins within a sample like gel electrophoresis does.