Alpha-helix

The alpha helix is the most common helix found in nature. It consists of a coiled polypeptide chain, in which the side chains of the amino acids extend outward from the core, this allows it to maintain its shape. They can be found in many different types of proteins, from globular proteins, such as myoglobin to keratin, which is a fibrous protein. Both these are prodominantly alpha helical in structure. The strength of the helix is determined by the number of disulphide bonds between the different turns of the helix.

References

Champe, Pamela C.  Biochemistry, 4th Edition. United States of America, Lippincott Williams &Wilkins, 2008.