Axis bending

Bacteria come in three shapes spherical (coccus), rod-shaped (baciUus), and spiral-shaped (vibrio, spirillum, and spirochete). A vibrio is a spiral organism shaped like a coma. A spirillum is also a spiral organism whose long axis remains rigid when in motion the spirochete is also yet another spiral organism whose long axis bends when in motion. 

Spirochete—An organism whose long axis bends when in motion. 

Fig. 27 Shape distortion of ferrogels due to non-uniform magnetic field, a No external magnetic field, b The maximal field strength is located under the lower end of the gel. c The maximal field strength is focused in the middle of the gel along its axis, bending induced by a permanent magnet...

Another limitation is the assumption that in the ground state the axis is a straight line. There are special sequences in which the DNA axis bends. These are clusters (dA) (dT) with n=4- -6 [84W1, 85D1, 85H1, 86D1, 86K1]. However, these clusters have to be repeated with the periodicity of the double helix in order to influence the properties of DNA. In most cases, there is not such a periodicity and the elastic rod model holds. 

DNA bending is yet another index of interest. MD Toolchest provides two tools, Bending Dials and Persistence Analysis, to characterize bends in the DNA helical axis. Bending Dials calculates stepwise DNA bending... 

The deformation of the DNA double helix plays an important role in structural biology, and the molecular nature of sequence-dependent axis bending, both intrinsic and induced. 

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