side chain (R group)

l amino acid

dipolar ion (zwitterion)

peptide bond (amide bond)

disulfide bond

primary structure

torsion angle

phi (ϕ) angle

psi (ψ) angle

Ramachandran plot

secondary structure

α helix

rise (translation)

β pleated sheet

β strand

63

reverse turn (β turn; hairpin turn)

coiled coil

heptad repeat

tertiary structure

motif (supersecondary structure)

domain

subunit

quaternary structure

cooperative transition

intrinsically unstructured protein (IUP)

metamorphic protein

prion