Which of the following statement about 2D gel electrophoresis is correct?

(a) SDS gel electrophoresis and isoelectric focusing both separate native proteins
(b) SDS gel electrophoresis and isoelectric focusing both make use of the migration of proteins in an electric field
(c) SDS gel electrophoresis and isoelectric focusing both require a ph gradient
(d) SDS gel electrophoresis and isoelectric focusing together make up the process of 2D gel electrophoresis

✅ Correct answer: (D) SDS gel electrophoresis and isoelectric focusing together make up the process of 2D gel electrophoresis

Explanation:

2D gel electrophoresis (Two-Dimensional Gel Electrophoresis) is a technique that combines Isoelectric Focusing (IEF) and SDS-PAGE to separate proteins based on two properties: charge and size.

Steps in 2D Gel Electrophoresis:

1. First dimension: Isoelectric Focusing (IEF)

   • Proteins are separated based on their isoelectric point (pI) in a pH gradient.
   • Proteins migrate in an electric field until they reach their pI, where they have no net charge and stop moving.

2. Second dimension: SDS-PAGE

   • The separated proteins from IEF are then treated with SDS, which gives them a uniform negative charge.
   • They are separated based on molecular weight (size) in the polyacrylamide gel.
   • Smaller proteins migrate farther, and larger proteins move slower.

Together, these two techniques (IEF and SDS-PAGE) form 2D gel electrophoresis, allowing high-resolution protein separation.

Why Not the Other Options?

• (A) SDS gel electrophoresis and isoelectric focusing both separate native proteins ❌

  • Incorrect, because SDS-PAGE denatures proteins, while IEF can be done under denaturing or native conditions.
  • In 2D-PAGE, SDS-PAGE is used after IEF, so the final proteins are denatured, not native.

• (B) SDS gel electrophoresis and isoelectric focusing both make use of the migration of proteins in an electric field ❌

  • Partially true, but incomplete.
  • Both techniques involve electrophoresis (movement in an electric field), but they separate proteins based on different principles (charge in IEF, size in SDS-PAGE).

• (C) SDS gel electrophoresis and isoelectric focusing both require a pH gradient ❌

  • Incorrect, because only IEF requires a pH gradient.
  • SDS-PAGE does not use a pH gradient; it separates proteins based on size using SDS.

Final Answer:

✅ (D) SDS gel electrophoresis and isoelectric focusing together make up the process of 2D gel electrophoresis