Why is the helix such a popular shape?

February 18, 2005

Perhaps because they are nature's space savers

Something about nature loves a helix, the ubiquitous spiral shape taken on by DNA and many other molecules found in the cells of living creatures. The shape is so useful that, while researching the means of creating self-assembling artificial helices, physicists at the University of Pennsylvania believe that they have come across a plausible mathematical reason for why the helical shape is so common. Their findings appear in the Feb. 18 issue of the journal Science.

"The classic answer is that helices are helical because the shape is dictated by bonds between molecules. But that only answers how a helix is formed and not why they are that shape," said Randall Kamien, a professor in Penn's Department of Astronomy and Physics. "It turns out that a helix, essentially, is a great way to bunch up a very long molecule, such as DNA, in a crowded place, such as a cell."

In the dense environment of the cell, long molecular chains frequently adopt ordered helical conformations. Not only does this enable information to be tightly packed, as in DNA, but it also forms a surface that allows molecules, such as the machines that enable DNA transcription and repair, to grapple on to it at regular intervals.

To picture how space matters to the formation of helices, Kamien and graduate student Yehuda Snir envisioned the system as a flexible, unbreakable tube immersed in a mixture of hard spheres, analogous to a molecule in a very crowded cell. As they saw it, the space occupied by the tube is space that could be otherwise occupied by the spheres. They find that the best shape for the short flexible tube Ц the conformation that takes the least amount of energy and takes up the least space Ц is that of a helix with a geometry close to that found in natural helices.

"It would seem that the success of the helix as a shape in biological molecules is a case of nature working the best it can with the constraints at hand," Kamien said. "The spiral shape of DNA is dictated by the space available in a cell much like the way the shape of a spiral staircase is dictated by the size of an apartment."

Source: University of Pennsylvania

Explore further: Helically twisted photonic crystal fibres

Related Stories

Helically twisted photonic crystal fibres

July 7, 2017

Photonic crystal fibres (PCF) are strands of glass, not much thicker than a human hair, with a lattice of hollow channels running along the fibre. If they are continuously twisted in their production, they resemble a multi-helix. ...

Scientists discovers 'firework' display in Helix Nebula

July 20, 2009

(PhysOrg.com) -- A star does not die without getting noticed and may even leave the universe with "fireworks." At the end of its life cycle, a star begins to collapse in the middle and throws new material into space. The ...

Into the eye of the helix

February 25, 2009

(PhysOrg.com) -- The Helix Nebula, NGC 7293, lies about 700 light-years away in the constellation of Aquarius (the Water Bearer). It is one of the closest and most spectacular examples of a planetary nebula.

Recommended for you

Genome study offers clues about history of big cats

July 21, 2017

(Phys.org)—A large international team of researchers has conducted a genetic analysis and comparison of the world's biggest cats to learn more about their history. In their paper published on the open source site Science ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.