Alfaheliksi

Alfaheliksi is the Finnish term for the alpha helix, a widespread secondary structure in proteins. In three-dimensional protein structures, alfaheliksi describes a right-handed coil formed when backbone hydrogen bonds stabilize the pattern between the carbonyl oxygen of residue i and the amide hydrogen of residue i+4. The canonical alpha helix contains about 3.6 amino acids per turn, with a rise of roughly 1.5 Å per residue and a pitch near 5.4 Å. Side chains extend outward from the helical axis, giving the helix an often amphipathic character in many sequences.

Alfaheliksi is a common element in globular proteins and in structural motifs such as helix bundles and coiled-coils. It contributes to overall protein stability and can influence folding pathways and interaction interfaces. Proline and glycine are notable exceptions: proline can disrupt regular hydrogen bonding and terminate helices, while glycine provides conformational flexibility that can destabilize or permit alternative conformations.

The term derives from the English “alpha helix” and is used in Finnish-language textbooks and scientific writing. It may be written as alfaheliksi or alfa-heliksi depending on style guidelines. In multilingual contexts, the term is typically linked to discussions of secondary structure, protein folding, and structural biology.

See also: Alpha helix, protein folding, secondary structure, coiled-coil.