Protein Structure, Secondary

**Definition:** The level of protein structure in which regular hydrogen-bond interactions within contiguous stretches of polypeptide chain give rise to ALPHA-HELICES; BETA-STRANDS (which align to form BETA-SHEETS), or other types of coils. This is the first folding level of protein conformation.

**Tree numbers:** - G02.111.570.820.709.600

**Synonyms:** - Secondary Protein Structure