None Not seen in alpha helix ?
Ans. is 'c' i.e., Proline Proline is never found in a-helix as it has imino group (-NH) not amino (-N112).Thus it cannot provide hydrogen for hydrogen bonding, the major stabilizing force of a-helix.Glycine also tends to disrupt a-helix; because of its high flexibility and small size it often induces bends in a-helix.
Alanine
Leucine
Proline
Isoleucine