What contracts effect the stability of a a-helix?

-Not all polypeptide sequences adopt a-helical structures -Small hydrophobic residues such as Ala and Leu are strong helix formers -Pro acts as a helix breaker because the rotation around the N-Ca bond is impossible -Gly acts as a helix breaker because the tiny R-group supports other conformations -Attractive or repulsive interactions between side chains 3–4 amino acids apart will affect formation.