The helical structure of protein is stabilised by:

Options

A. Peptide bonds
B. Hydrogen bonds
C. Dipeptide bonds
D. van der Waals' forces

Answer

**Step-by-Step Solution:**

1. **Understand the Structure of Proteins:**
- Proteins have different levels of structure: primary, secondary, tertiary, and quaternary. The helical structure referred to in the question is known as the alpha helix, which is part of the secondary structure of proteins.

2. **Identify the Stabilizing Forces:**
- The stability of the alpha helix is primarily due to specific interactions between the amino acid residues within the protein.

3. **Focus on Hydrogen Bonds:**
- In the alpha helix, hydrogen bonds form between the carbonyl oxygen (C=O) of one amino acid and the amide hydrogen (N-H) of another amino acid that is four residues earlier in the sequence. This bonding pattern is crucial for maintaining the helical shape.

4. **Conclusion:**
- Therefore, the helical structure of proteins, specifically the alpha helix, is stabilized by hydrogen bonding between the NH (amide) and CO (carbonyl) groups of the amino acids.

**Final Answer:**
The helical structure of protein is stabilized by hydrogen bonding.

---