Entropic boundary effects on the elasticity of short DNA molecules

Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Aug;80(2 Pt 1):020903. doi: 10.1103/PhysRevE.80.020903. Epub 2009 Aug 24.


We have measured the entropic elasticity of double-stranded-DNA molecules ranging from 247 to 1298 bp in length using axial force-clamp optical tweezers. We show that entropic end effects and excluded-volume forces from surface attachments become significant for such short molecules. The effective persistence length of the shortest molecules decreases by a factor of 2 compared to the established value for long molecules, and excluded-volume forces extend the molecules to about one third of their nominal contour length. We interpret these results in the framework of an inextensible semiflexible rod model.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • DNA / chemistry*
  • Elasticity*
  • Entropy*
  • Optical Tweezers
  • Surface Properties


  • DNA