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  2. Helix - Wikipedia

    en.wikipedia.org/wiki/Helix

    A helix (/ ˈhiːlɪks /; pl. helices) is a shape like a cylindrical coil spring or the thread of a machine screw. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures ...

  3. Alpha helix - Wikipedia

    en.wikipedia.org/wiki/Alpha_helix

    An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix). The alpha helix is the most common structural arrangement in the secondary structure of proteins. It is also the most extreme type of local structure, and it is the local structure that is most easily predicted from a sequence of amino ...

  4. Spiral - Wikipedia

    en.wikipedia.org/wiki/Spiral

    Cutaway of a nautilus shell showing the chambers arranged in an approximately logarithmic spiral. In mathematics, a spiral is a curve which emanates from a point, moving farther away as it revolves around the point. [1][2][3][4] It is a subtype of whorled patterns, a broad group that also includes concentric objects.

  5. Helix angle - Wikipedia

    en.wikipedia.org/wiki/Helix_angle

    Helix angle. In mechanical engineering, a helix angle is the angle between any helix and an axial line on its right, circular cylinder or cone. [1] Common applications are screws, helical gears, and worm gears. The helix angle references the axis of the cylinder, distinguishing it from the lead angle, which references a line perpendicular to ...

  6. Triple helix - Wikipedia

    en.wikipedia.org/wiki/Triple_helix

    Triple helix. The collagen triple helix is a triple helix formed from three separate protein helices, spiraling around the same axis. In the fields of geometry and biochemistry, a triple helix (pl.: triple helices) is a set of three congruent geometrical helices with the same axis, differing by a translation along the axis.

  7. Triple-stranded DNA - Wikipedia

    en.wikipedia.org/wiki/Triple-stranded_DNA

    Triple-stranded DNA (also known as H-DNA or Triplex-DNA) is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In triple-stranded DNA, the third strand binds to a B-form DNA (via Watson–Crick base-pairing) double helix by forming Hoogsteen base pairs or reversed Hoogsteen hydrogen bonds.

  8. Helix Nebula - Wikipedia

    en.wikipedia.org/wiki/Helix_nebula

    General information. The Helix Nebula is an example of a planetary nebula, formed by an intermediate to low-mass star, which sheds its outer layers near the end of its evolution. Gases from the star in the surrounding space appear, from Earth's perspective, a helix structure. The remnant central stellar core, known as the central star (CS) of ...

  9. Helix-turn-helix - Wikipedia

    en.wikipedia.org/wiki/Helix-turn-helix

    The helix-turn-helix (HTH) is a major structural motif capable of binding DNA. Each monomer incorporates two α helices, joined by a short strand of amino acids, that bind to the major groove of DNA. The HTH motif occurs in many proteins that regulate gene expression. It should not be confused with the helix–loop–helix motif.