APS (Ammonium persulphate) is used in SDS-PAGE for

(A) preventing oxidation
(B) cross-linking
(C) its role as a catalyst
(D) free radical formation

Correct answer: (D) Free radical formation

Explanation:

Ammonium persulfate (APS) is a crucial component in SDS-PAGE because it helps in the polymerization of acrylamide to form the gel matrix.

• APS acts as an initiator by generating free radicals.
• When combined with TEMED (Tetramethylethylenediamine), APS decomposes into sulfate radicals, which initiate the polymerization of acrylamide and bisacrylamide to form the polyacrylamide gel.

Why Not the Other Options?

• (A) Preventing oxidation ❌

  • APS does not prevent oxidation; instead, it produces oxidative free radicals for polymerization.

• (B) Cross-linking ❌

  • Bisacrylamide (not APS) is responsible for cross-linking in SDS-PAGE.

• (C) Its role as a catalyst ❌

  • APS is not exactly a catalyst; it acts as a radical initiator.
  • TEMED is the actual catalyst that accelerates APS decomposition to generate free radicals.

Final Answer:

✅ (D) Free radical formation