Journal article
The geometrical origin of the strain-twist coupling in double helices
A simple geometrical explanation for the counterintuitive phenomenon when twist leads to extension in double helices is presented. The coupling between strain and twist is investigated using a tubular description. It is shown that the relation between strain and rotation is universal and depends only on the pitch angle.
For pitch angles below 39.4◦ strain leads to further winding, while for larger pitch angles strain leads to unwinding. The zero-twist structure, with a pitch angle of 39.4◦, is at the unique point between winding and unwinding and independent of the mechanical properties of the double helix. The existence of zero-twist structures, i.e. structures that display neither winding, nor unwinding under strain is discussed.
Close-packed double helices are shown to extend rather than shorten when twisted. Numerical estimates of this elongation upon winding are given for DNA, chromatin, and RNA.
Language: | English |
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Publisher: | AIP Publishing LLC |
Year: | 2011 |
Pages: | 012108 |
ISSN: | 21583226 |
Types: | Journal article |
DOI: | 10.1063/1.3560851 |