Direct Determination of DNA Twist-Stretch Coupling
  The symmetries of the DNA double helix require a new term in its linear response to stress: the coupling between twist and stretch. Recent experiments with torsionally-constrained single molecules give the first direct measurement of this important material parameter. We extract its value from a recent experiment of Strick et al. [Science 271 (1996) 1835] and find rough agreement with an independent experimental estimate recently given by Marko. We also present a very simple microscopic theory predicting a value comparable to the one observed. 
Randall D. Kamien, Tom C. Lubensky, Philip Nelson, and Corey S. O'Hern