✅ Correct answer: (D) Using a support medium with lower charge

Explanation:

Electroendosmotic flow (EOF) occurs due to the interaction between the charged support medium (agarose) and the buffer ions in electrophoresis. This buffer flow can disrupt protein migration and affect separation accuracy.

• Agarose gels have negatively charged groups (e.g., sulfate and carboxyl groups) that attract positive ions from the buffer, leading to buffer movement (EOF) in the opposite direction of protein migration.
• Using a support medium with lower charge (e.g., modified agarose with fewer negative charges) reduces EOF, allowing proteins to migrate more predictably.

Why Not the Other Options?

• (A) Applying less amount of sample ❌

  • The sample volume affects band sharpness, but it does not influence EOF, which is caused by the gel itself.

• (B) Increasing the voltage ❌

  • Higher voltage can actually increase EOF, making the issue worse rather than reducing it.

• (C) Running the gel at low temperature ❌

  • Lower temperature reduces diffusion and Joule heating, but EOF is primarily determined by the charge of the gel, not temperature.

Final Answer:

✅ (D) Using a support medium with lower charge