Two dimensional gel electrophoresis is a technique for separating proteins

(A) Based on charge
(B) Based on mass
(C) Based on both charge and mass
(D) Based on its pI value

Correct answer: (C) Based on both charge and mass

Explanation:

Two-Dimensional Gel Electrophoresis (2D-PAGE) is a powerful technique used for protein separation by combining two different electrophoretic methods:

1. First Dimension: Isoelectric Focusing (IEF)

   • Proteins are separated based on their isoelectric point (pI) (the pH at which the protein has no net charge).
   • This means proteins migrate according to charge until they reach their pI value, where they stop moving.

2. Second Dimension: SDS-PAGE

   • After IEF, the proteins are further separated using SDS-PAGE, which sorts proteins based on molecular mass.
   • SDS denatures the proteins and gives them a uniform negative charge, ensuring separation depends only on size.

Thus, 2D-PAGE separates proteins based on both charge (first dimension) and mass (second dimension).

Why Not the Other Options?

• (A) Based on charge ❌

  • Only the first step (IEF) separates based on charge.
  • But 2D-PAGE also includes mass separation in the second step.

• (B) Based on mass ❌

  • Only the second step (SDS-PAGE) separates based on mass.
  • Charge separation (IEF) is also crucial in 2D-PAGE.

• (D) Based on its pI value ❌

  • pI (isoelectric point) is used in the first step (IEF), but the second step further separates proteins by mass.

Final Answer:

✅ (C) Based on both charge and mass