Q.16 After electrophoresis, the gel containing the separated proteins is immersed in an acid alcoholic solution of the dye. This:

1. Denatures the proteins
2. Fixes them in the gel
3. Ensures they do not wash out
4. Allows dye to bind them

Choose the correct answer from the options given below:

1. (A), (C) and (D) only
2. (A), (B) and (C) only
3. (A), (B), (C) and (D)
4. (B), (C) and (D) only

   After electrophoresis, immersing the gel in acid-alcoholic dye solution primarily fixes proteins and prepares them for staining while preventing diffusion.

   Option Breakdown

   The process refers to standard protein gel staining protocols like Coomassie Brilliant Blue, where fixation occurs before or simultaneously with dye immersion.

   • (A) Denatures the proteins: Incorrect. Acid-alcohol conditions the gel and precipitates proteins but doesn’t primarily denature them (they’re already denatured by SDS during electrophoresis).

   • (B) Fixes them in the gel: Correct. Acidic alcohol fixes/precipitates proteins, preventing diffusion out of the gel matrix.

   • (C) Ensures they do not wash out: Correct. Fixation immobilizes proteins so they stay in place during subsequent washing/destaining.

   • (D) Allows dye to bind them: Correct. Acid-alcohol creates conditions (protonation, dehydration) for optimal dye-protein binding, especially for Coomassie.

   Answer: (B), (C) and (D) only.

   Electrophoresis Gel Staining Process Explained

   Electrophoresis gel staining acid alcoholic dye treatment after protein separation serves multiple roles in visualizing bands for biochemistry analysis, crucial for GATE Life Sciences. This step uses methanol/acetic acid with Coomassie dye to immobilize proteins in polyacrylamide/SDS-PAGE gels.

   Step-by-Step Mechanism

   1. Fixation: Acid dehydrates gel and precipitates proteins via methanol/acetic acid.

   2. Immobilization: Prevents protein diffusion during washes (no washout).

   3. Dye Binding: Protonates proteins for electrostatic/hydrophobic Coomassie attachment.

   Purpose	Role of Acid-Alcoholic Dye	GATE Relevance
   (B) Fixes proteins	Precipitates in gel matrix	SDS-PAGE protocol
   (C) No washout	Immobilizes bands	Staining accuracy
   (D) Dye binding	Enables Coomassie interaction	Band visualization
   (A) Denatures	Not primary (already SDS-denatured)	Common misconception

   GATE Exam Tips

   Focus on Coomassie protocol sequence: electrophoresis → fixation/staining → destaining. Silver staining skips alcohol but uses similar fixation. Practice PYQs testing “after electrophoresis” steps for molecular biology scoring.