The helical axes have significantly different directions in the two structures, and it is not possible to superimpose the helices.

With the line of sight being the helical axis, if clockwise movement of the helix corresponds to axial movement away from the observer, then it is called a right-handed helix.

The optimal helical axis is shown in each case.

Here, the strands turn about the helical axis in a left-handed spiral, the opposite of the more common B form.

In a "relaxed" double-helical segment of B-DNA, the two strands twist around the helical axis once every 10.4-10.5 base pairs of sequence.

For the case of Bragg reflection only the lowest-order reflection is allowed if the light is incident along the helical axis, whereas for oblique incidence higher-order reflections become permitted.

For almost one hundred years, scientists assumed that the most stable cholesteric helical structure could be described by a single helical axis about which the director rotates.

Although an unlimited number of helical axes are actually present, this structure was named double twist structure.