triple helix

(noun)

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.

Related Terms

Examples of triple helix in the following topics:

  • Structural Elements of Connective Tissue

    • Collagen is a composed of a triple helix , which generally consists of two identical chains (α1) and an additional chain that differs slightly in its chemical composition (α2).
    • In bone, entire collagen triple helices lie in a parallel, staggered array.
    • Model of the collagen triple helix.

  • The DNA Double Helix

    • The DNA double helix looks like a twisted staircase, with the sugar and phosphate backbone surrounding complementary nitrogen bases.
    • DNA has a double-helix structure, with sugar and phosphate on the outside of the helix, forming the sugar-phosphate backbone of the DNA.
    • The two strands of the helix run in opposite directions, so that the 5′ carbon end of one strand faces the 3′ carbon end of its matching strand.
    • During DNA replication, each strand is copied, resulting in a daughter DNA double helix containing one parental DNA strand and a newly synthesized strand.
    • Native DNA is an antiparallel double helix.

  • Covalent Bonds and Other Bonds and Interactions

    • Its biosynthesis involves breaking the triple bond of molecular nitrogen, or N2, followed by the formation of several carbon-nitrogen single and double bonds.
    • One, two, or three pairs of electrons may be shared between two atoms, making single, double, and triple bonds, respectively.
    • Thus, triple bonds are the strongest.
    • Molecular nitrogen consists of two nitrogen atoms triple bonded to each other.
    • For example, hydrogen bonds are responsible for zipping together the DNA double helix.

  • Naming Alkenes and Alkynes

    • Alkenes and alkynes are named similarly to alkanes, based on the longest chain that contains the double or triple bond.
    • Alkenes are hydrocarbons that contain one or more double bonds, while alkynes contain one or more triple bonds.
    • Alkene and alkyne compounds are named by identifying the longest carbon chain that contains both carbons of the double or triple bond.
    • The carbon backbone is numbered from the end that yields the lowest positioning for the double or triple bond.
    • For multiple double or triple bonds, "di-," "tri-," or "tetra-" can be added prior to the "-ene" or "-yne."

  • The Structure and Sequence of DNA

    • DNA is a double helix of two anti-parallel, complementary strands having a phosphate-sugar backbone with nitrogenous bases stacked inside.
    • Watson and Crick proposed that DNA is made up of two polynucleotide strands that are twisted around each other to form a right-handed helix.
    • The diameter of the DNA double helix is 2 nm and is uniform throughout.
    • Therefore, ten base pairs are present per turn of the helix.
    • DNA has (a) a double helix structure and (b) phosphodiester bonds.

  • Triple Integrals

    • For $T \subseteq R^3$, the triple integral over $T$ is written as $\iiint_T f(x,y,z)\, dx\, dy\, dz$.
    • For $T \subseteq R^3$, the triple integral over $T$ is written as
    • Notice that, by convention, the triple integral has three integral signs (and a double integral has two integral signs); this is a notational convention which is convenient when computing a multiple integral as an iterated integral.
    • The extension of those formulae to triple integrals should be apparent.
    • By calculating the triple integral of the constant function 1 over the parallelepiped itself: $\iiint_\mathrm{parallelepiped} 1 \, dx\, dy\, dz$

  • Double and Triple Covalent Bonds

    • Double and triple bonds, comprised of sigma and pi bonds, increase the stability and restrict the geometry of a compound.
    • A triple bond involves the sharing of six electrons, with a sigma bond and two $\pi$ bonds.
    • The simplest triple-bonded organic compound is acetylene, C2H2.
    • Similar to double bonds, no rotation around the triple bond axis is possible.
    • Describe the types of orbital overlap that occur in single, double, and triple bonds

  • The Secondary & Tertiary Structures of DNA

    • The double helix is further stabilized by hydrophobic attractions and pi-stacking of the bases.
    • The helix shown here has ten base pairs per turn, and rises 34 Å (3.4 nm) in each turn.
    • This right-handed helix is the favored conformation in aqueous systems, and has been termed the B-helix.
    • Topoisomerase: This enzyme initiates unwinding of the double helix by cutting one of the strands.
    • Separation of a portion of the double helix takes place at a site called the replication fork.

  • Solid to Gas Phase Transition

    • But at temperatures below that of the triple point, a decrease in pressure will result in a phase transition directly from the solid to the gaseous.
    • Also, at pressures below the triple point pressure, an increase in temperature will result in a solid being converted to gas without passing through the liquid region.
    • This is because the pressure of their triple point is very high and it is difficult to obtain them as liquids.
    • Notice the triple point of the substance.
    • At temperatures and pressures below those of the triple point, a phase change between the solid and gas phases can take place.

  • Secondary & Tertiary Structure of Large Peptides and Proteins

    • The other diagrams display a ball & stick model and a ribbon that defines this α-helix.
    • The alpha-helix is right-handed, which means that it rotates clockwise as it spirals away from a viewer at either end.
    • Using the dihedral angle terminology noted above, a perfect α-helix has Φ = -58º and Ψ = -47º.
    • Using this terminology, the alpha-helix is a 3.613 helix.
    • A large section of antiparallel beta-sheets is colored violet, and a short alpha-helix is green.