Question

In the enzyme-linked antibody used in ELISA, the interaction between the enzyme and antibody is stabilized by

• A. Hydrogen bond
• B. Ionic bond
• C. Covalent bond
• D. Van der waals interactions

Hint:

In molecular biology, when two biomolecules are meant to be permanently joined to create a single functional unit (like a conjugate for an assay), the linkage is almost always covalent. Non-covalent bonds are typically for reversible interactions like binding and recognition.

Answer 1

The Correct Option is C

Step 1: Introduction to ELISA:
ELISA (Enzyme-Linked Immunosorbent Assay) uses an antibody linked to a reporter enzyme. This enzyme triggers a detectable color change or fluorescence. The question concerns the type of bond linking the enzyme to the antibody.
Step 2: Bond Type Analysis:
The bond between the antibody and enzyme must be strong and durable to withstand storage, washing, and the assay process.
Hydrogen bonds, Ionic bonds, and Van der Waals interactions are non-covalent interactions. Although important for protein structure and antigen-antibody binding, they are individually weak and reversible. They are insufficient to create a permanent, stable link between the antibody and the enzyme for a diagnostic assay.
A Covalent bond involves shared electrons, resulting in a strong, stable chemical bond. In biotechnology, chemical cross-linking agents (e.g., glutaraldehyde, SMCC) are used to create permanent covalent bonds between functional groups on the antibody and enzyme. This ensures the enzyme remains attached throughout the ELISA.
Step 3: Conclusion:
The stable interaction in an enzyme-antibody conjugate is a covalent bond formed through a chemical reaction.