Question

In SDS-PAGE, the proteins are separated mainly based on

• A. Molecular sieving effect
• B. Charge/mass ratio
• C. Partition principle
• D. Adsorption principle

Hint:

In native PAGE, proteins separate based on both charge and size. In SDS-PAGE, the charge is masked by SDS, making the separation depend solely on the molecular sieving effect (size/mass).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Sodium Dodecyl Sulphate-Polyacrylamide Gel Electrophoresis (SDS-PAGE) is a technique used to analyze proteins by separating them according to their molecular weight.

Step 2: Detailed Explanation:
1. SDS is an anionic detergent that denatures proteins and binds to them, imparting a uniform negative charge-to-mass ratio.
2. Because the charge density is identical for all proteins in the sample, electrostatic charge does not drive separation.
3. When an electric field is applied, the proteins migrate through the porous polyacrylamide gel matrix.
4. Smaller proteins pass easily through the pores, while larger proteins are impeded. This separation based on physical size within a molecular meshwork is called the molecular sieving effect.

Step 3: Final Answer:
The separation of proteins in SDS-PAGE is governed by the molecular sieving effect.