Question

investigators are studying a protein that must be phosphorylated to be activated. which method could be used to separate the phosphorylated form of the protein from the form that lacks an activating phosphate group?
choose one:
○ a. equilibrium sedimentation
○ b. gel - filtration chromatography
○ c. differential centrifugation
○ d. velocity sedimentation
○ e. ion - exchange chromatography

Explanation:

• Equilibrium sedimentation: Used to determine the molecular weight and density of macromolecules by centrifugation until equilibrium is reached. Not suitable for separating based on phosphorylation (charge difference).
• Gel - filtration chromatography: Separates molecules based on size. Phosphorylation may not cause a significant enough size difference for this method to be effective.
• Differential centrifugation: Separates components based on size and density by a series of centrifugation steps. Not targeted at charge differences (like phosphorylation).
• Velocity sedimentation: Separates particles based on their sedimentation rate (related to size and shape). Again, not focused on charge.
• Ion - exchange chromatography: Relies on the charge of molecules. Phosphorylation adds a negatively - charged phosphate group. So, the phosphorylated protein (more negatively charged) and non - phosphorylated protein (less negatively charged) can be separated based on their interaction with the ion - exchange resin.

Answer:

E. ion - exchange chromatography