2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/151653The 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. 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.7 Pages, plain LaTeX, 1 included eps figure. To appear in the Proceedings of The Syposium on Statistical Mechanics in Physics and Biology, MRS 1996 Fall MeetingSoft Condensed MatterQuantitative Biologytext