Abstract
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.
Original language | English |
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Article number | 012108 |
Journal | A I P Advances |
Volume | 1 |
Number of pages | 7 |
ISSN | 2158-3226 |
DOIs | |
Publication status | Published - 2011 |
Keywords
- DNA
- Proteins
- Molecular biophysics
- Molecular configurations
- Biomechanics