Chymotrypsinogen in the native state and reduced unfolded sates is loaded in well A and B respectively. They are
electrophoreses and stain, one of the following results is likely to be observed.

a. Protein in well A would have moved longer distance than that in well B
b. Protein in well A would have moved shorter distance than that in well B
c. Protein in well A and B would have moved the same distance
d. Protein in well A and B would not move at all

The correct answer is:

✅ (b) Protein in well A would have moved a shorter distance than that in well B

Explanation:

Chymotrypsinogen is a globular protein that can exist in:

• Native (folded) state → More compact structure
• Reduced (unfolded) state → Fully extended structure due to the disruption of disulfide bonds

In SDS-PAGE, proteins migrate based on their size (molecular weight), but shape also plays a role in migration distance.

1. Well A (Native Chymotrypsinogen)

   • In its folded state, the protein remains more compact.
   • This results in less interaction with SDS, leading to less migration.

2. Well B (Reduced & Unfolded Chymotrypsinogen)

   • When the protein is denatured (unfolded) using reducing agents (e.g., β-mercaptoethanol or DTT), the disulfide bonds are broken.
   • The protein fully extends, allowing more SDS molecules to bind, giving it a higher charge-to-mass ratio.
   • This leads to greater migration (moves farther down the gel) than the native protein.

Why Not the Other Options?

• (a) Protein in well A would have moved a longer distance than that in well B ❌ → Incorrect, because native (compact) proteins move less in SDS-PAGE.
• (c) Protein in well A and B would have moved the same distance ❌ → Incorrect, because folded vs. unfolded states affect migration.
• (d) Protein in well A and B would not move at all ❌ → Incorrect, because SDS imparts a negative charge, allowing proteins to migrate.

Conclusion:

Since the unfolded protein (well B) moves farther than the native protein (well A) in SDS-PAGE, the correct answer is:

✅ (b) Protein in well A would have moved a shorter distance than that in well B.