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: Understanding the Concept:
ELISA (Enzyme-Linked Immunosorbent Assay) relies on an antibody that has been conjugated (linked) to a reporter enzyme. This enzyme catalyzes a colorimetric or fluorometric reaction, allowing for detection. The question asks about the nature of the bond linking the enzyme to the antibody.
Step 2: Detailed Explanation:
The linkage between the antibody and the enzyme must be very stable and robust. The conjugate needs to withstand storage, multiple washing steps, and incubation during the assay without falling apart.
Hydrogen bonds, Ionic bonds, and Van der waals interactions are all non-covalent interactions. While they are crucial for protein folding and antigen-antibody binding, they are individually weak and reversible. They would not be strong enough to create a permanent, stable link between two separate protein molecules (the antibody and the enzyme) for use in a diagnostic assay.
A Covalent bond involves the sharing of electron pairs between atoms. These are strong, stable chemical bonds. In biotechnology, specific chemical cross-linking agents (like glutaraldehyde or SMCC) are used to form permanent covalent bonds between functional groups (e.g., amines, sulfhydryls) on the surfaces of the antibody and the enzyme. This ensures that the enzyme remains attached to the antibody throughout the entire ELISA procedure.
Step 3: Final Answer:
The stable interaction in an enzyme-antibody conjugate is a covalent bond formed through a chemical reaction.