The helical structure of protein is stabilised by:

Options

A. Peptide bond
B. Dipeptide bond
C. van der Waal 's forces
D. Hydrogen bond

Answer

To answer the question regarding what stabilizes the helical structure of proteins, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure**: The helical structure of proteins is commonly referred to as the alpha helix. This is a common secondary structure found in proteins.

2. **Understand the Role of Hydrogen Bonds**: The stability of the alpha helix is primarily due to hydrogen bonds. These bonds form between different parts of the same polypeptide chain.

3. **Locate the Specific Groups Involved**: In the alpha helix, hydrogen bonds occur between the NH (amide) group of one amino acid and the carbonyl oxygen (C=O) of another amino acid that is typically four residues earlier in the sequence.

4. **Explain the Mechanism**: The hydrogen bonding pattern helps to maintain the helical shape by holding the backbone of the protein in a specific configuration, which is crucial for the protein's overall structure and function.

5. **Conclude with the Correct Answer**: Therefore, the helical structure of protein is stabilized by hydrogen bonds.

### Final Answer:
The helical structure of protein is stabilized by hydrogen bonds.

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