Triple helix
Encyclopedia
In geometry
Geometry
Geometry arose as the field of knowledge dealing with spatial relationships. Geometry was one of the two fields of pre-modern mathematics, the other being the study of numbers ....

, a triple helix (plural triple helices) is a set of three congruent geometrical helices
Helix
A helix is a type of smooth space curve, i.e. a curve in three-dimensional space. It has the property that the tangent line at any point makes a constant angle with a fixed line called the axis. Examples of helixes are coil springs and the handrails of spiral staircases. A "filled-in" helix – for...

 with the same axis, differing by a translation along the axis. Structures in the form of a triple helix include:
  • collagen helix
    Collagen helix
    In collagen, the collagen helix, or type-2 helix, is a major shape in secondary structure. It consists of a triple helix made of the repetitious amino acid sequence glycine - X - Y, where X and Y are frequently proline or hydroxyproline....

  • peptide nucleic acid (some types, not all)
  • triple-stranded DNA
    Triple-stranded DNA
    A triple-stranded DNA is a structure of DNA in which three oligonucleotides wind around each other and form a triple helix. In this structure, one strand binds to a B-form DNA double helix through Hoogsteen or reversed Hoogsteen hydrogen bonds....

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