Question

The polymerization of the gel used in polyacrylamide gel electrophoresis occurs between acrylamide and

• A. Tetra bis acrylamide
• B. N, N'-acrylamide
• C. N, N'-Methylene bis-acrylamide
• D. Methylene acrylamide

Hint:

In PAGE gels, a standard 29:1 or 35:1 ratio of acrylamide to bis-acrylamide is used to balance mechanical strength and pore size for optimal protein separation.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Polyacrylamide gel electrophoresis (PAGE) is a common molecular biology technique used to separate proteins and nucleic acids based on their size.
The gel is a cross-linked polymer network formed by the free-radical polymerization of monomer units in an aqueous buffer.

Step 2: Detailed Explanation:
The polyacrylamide gel matrix is formed by co-polymerizing two main components: acrylamide and a cross-linking agent.
Acrylamide monomers polymerize head-to-tail into long, linear chains.
By itself, polymerized acrylamide forms a viscous solution but not a gel.
To form a solid gel matrix with defined pores, a cross-linking agent is added.
The standard cross-linking agent used is N, N'-Methylene bis-acrylamide (commonly referred to as "bis-acrylamide").
Bis-acrylamide consists of two acrylamide residues joined by a methylene group.
During polymerization, the two vinyl groups of bis-acrylamide can be incorporated into different growing polyacrylamide chains, linking them together.
This cross-linking creates a three-dimensional mesh network.
The ratio of acrylamide to bis-acrylamide determines the pore size of the gel: a higher total concentration ($\%T$) and cross-linker concentration ($\%C$) produce smaller pores, which are used to resolve smaller biomolecules.
This free-radical reaction is initiated by ammonium persulfate (APS) and catalyzed by tetramethylethylenediamine (TEMED).

Step 3: Final Answer:
The polymerization reaction occurs between acrylamide and the cross-linker N, N'-Methylene bis-acrylamide.