Question

How does an alpha-helical dipole form?

Answer 1

Alpha - helix is the most common type of secondary structure of globular protein. It has a right - hand coiled or spiral orientation in which each amino acid residue corresponds to a 100 degree turn in each helix has 3.6 residues per turn. The rise in the length of helix per turn is 1.5 A⁰. Hence rise in the length of helix per turn is 1.5 A⁰ x 3.6 = 5.4 A⁰. Helix formation is thermodynamically stable process with liberation of heat.

The repeated intermolecular hydrogen bond formed between the atoms in the peptide backbone ( - C=O - - - H - N -) is the main feature of alpha - helical structure. Every backbone -N-H group forms intermolecular hydrogen bond with -C=O group.  These hydrogen bonds provide thermodynamic stabilization to the alpha - helix.