Question

Out of the following, which type of interaction is responsible for the stabilisation of $\alpha$ -helix structure of proteins?

• A. Ionic bonding
• B. Hydrogen bonding
• C. Covalent bonding
• D. vander Waals forces

Answer 1

The Correct Option is B

The stability of the $\alpha$-helix structure of proteins is primarily due to hydrogen bonding. Let's explore this concept step-by-step:

1. The $\alpha$-helix is a common secondary structure found in proteins. It is characterized by a right-handed coiled or spiral structure.
2. Within the $\alpha$-helix, the backbone N-H group of an amino acid forms a hydrogen bond with the C=O group of an amino acid located four residues earlier. This interaction helps to stabilize the helical structure.
3. Hydrogen Bonding: This is a type of attractive interaction between a hydrogen atom bound to a more electronegative atom (like N or O) and another electronegative atom. In proteins, the N-H ... O=C hydrogen bond is a key factor in maintaining the $\alpha$-helix structure.

Now, let's rule out the other options:

• Ionic Bonding: This involves attraction between oppositely charged ions, which is not the primary stabilizing interaction in $\alpha$-helices.
• Covalent Bonding: While covalent bonds form the primary structure of proteins (linking amino acids together), they do not stabilize secondary structures like the $\alpha$-helix.
• van der Waals Forces: These are weak attractions that may contribute to protein folding but are not the main stabilizing force for the $\alpha$-helix.

Thus, the correct answer is Hydrogen bonding, as it plays a critical role in holding the $\alpha$-helical structure together by forming stable bonds between successive turns of the helix.