Triple helix

Schematic of triple-stranded DNA

In geometry, a triple helix (plural triple helices) is a set of three congruent geometrical helices with the same axis, differing by a translation along the axis. As with a single helix, a triple helix may be characterized by its pitch and diameter.

Structures in the form of a triple helix include:

• Collagen helix^[1]
• Triple-stranded DNA^[2]
• Triple-threaded worm gears^[3] and screws^[4]

References

1. Engel, Jürgen; Bächinger, Hans Peter (2005), "Structure, Stability and Folding of the Collagen Triple Helix", in Brinckmann, Jürgen; Notbohm, Holger; Müller, P. K., Collagen: Primer in Structure, Processing and Assembly, Topics in Current Chemistry 247, pp. 7–33, doi:10.1007/b103818, ISBN 978-3-540-23272-8
2. Bernués, J.; Azorín, F. (1995), "Triple-stranded DNA", Nucleic Acids and Molecular Biology 9: 1–21, doi:10.1007/978-3-642-79488-9_1.
3. Rattan, S. S. (2009), Theory of Machines (3rd ed.), Tata McGraw-Hill Education, p. 370, ISBN 9781259081415.
4. Collins, Jack A.; Busby, Henry R.; Staab, George H. (2010), Mechanical Design of Machine Elements and Machines, John Wiley & Sons, p. 464, ISBN 9780470413036.