α – helix is stabilised by

The α-helix structure in proteins is stabilized by hydrogen bonds. These bonds occur between the oxygen atom in the carbonyl group of each amino acid and the hydrogen atom in the amino group of the amino acid four residues ahead in the sequence.

Here are the steps:

1. The α-helix is a common secondary structure in proteins, formed by the folding of the polypeptide chain into a right-handed spiral conformation.

2. This structure is held together by hydrogen bonds, which are interactions between a hydrogen atom attached to a highly electronegative atom (such as oxygen or nitrogen) and another electronegative atom.

3. In the α-helix, these hydrogen bonds occur between the oxygen atom in the carbonyl group (C=O) of each amino acid and the hydrogen atom in the amino group (N-H) of the amino acid four residues ahead in the sequence.

4. This regular pattern of hydrogen bonding causes the polypeptide chain to twist into a helical shape, with each turn of the helix encompassing 3.6 amino acid residues.

5. The hydrogen bonds are nearly parallel to the axis of the helix, which helps to stabilize the structure.

6. The side chains of the amino acids in the α-helix project outwards from the helix, which allows them to interact with other parts of the protein and the surrounding environment.

7. The stability of the α-helix is also influenced by the sequence of amino acids, with certain sequences being more favorable for the formation of an α-helix.