The main advantage of discontinuous buffer system in SDS and native PAGE is

(a) Conformation of protein is conserved
(b) Constantly maintain the charge of proteins
(c) Assist in migration of proteins
(d) Enhance resolution of separation

The correct answer is:

(d) Enhance resolution of separation

Explanation:

A discontinuous buffer system is commonly used in SDS-PAGE and native PAGE to improve the resolution of protein separation. This system consists of:

1. Stacking gel (low acrylamide concentration, pH ~6.8)
2. Resolving gel (higher acrylamide concentration, pH ~8.8)
3. Electrode buffer (higher ionic strength, pH ~8.3)

Why does it enhance resolution?

• In the stacking gel, proteins are concentrated into thin bands due to differences in ion mobility, creating a sharp starting zone.
• In the resolving gel, proteins separate based on size (SDS-PAGE) or charge (native PAGE), leading to better resolution and clearer band separation.

Why not the other options?

• (a) Conformation of protein is conserved → This applies to native PAGE, but a discontinuous buffer system is primarily used to enhance resolution.
• (b) Constantly maintain the charge of proteins → While buffer systems influence protein charge, the main purpose of discontinuous buffers is improving separation, not just maintaining charge.
• (c) Assist in migration of proteins → Buffers do help migration, but the primary benefit is sharp band formation and high resolution.

Thus, the correct answer is (d) Enhance resolution of separation ✅