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![[Figure 3]](yt5034fig3mag.jpg)
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Figure 3
Illustrations of [n1, n2] helical symmetry with respect to helical nets. In (a), an EM segment of the microtubule structure is shown in a wrapped helical net with [11, 3] symmetry. The corresponding flattened unwrapped helical net is demonstrated in (b). A section of the corresponding [11, 3] helical net is drawn in (c), with the x axis covering the helical circumference, a twist range of 2π and the y axis parallel to the helical axis, corresponding to the helical rise. The colored circular dots in the net are the asymmetric subunits and a solid line that passes through a set of dots is a helix. A helical net can be redefined by any two sets of lines with their intersections covering all dots. With n2 fixed at 3, there are ten additional sets of helices which can be used to define the same helical structure. See text for an explanation of why only limited sets of helices are feasible with n2 fixed at 3. In (c), feasible sets of helices are marked beside the dots with the value of n1 colored red. Two of the new helical nets with helical symmetry [8, 3] and [14, 3] are superimposed in (c). The individual lattice drawn under the helical nets is to help in the visualization of individual helical nets. |
![[Figure 3]](yt5034fig3.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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