  We had combined the Neukirch-Marko model that describes the extension, torque
and supercoiling in single, stretched and twisted DNA of infinite contour
length, with a form of the free energy suggested by Sinha and Samuels to
describe short DNA, with contour length only a few times the persistence
length. We find that the free energy of the stretched but untwisted DNA, is
significantly modified from its infinitely length value and this in turn
modifies significantly the torque and supercoiling. We show that this is
consistent with short DNA being more flexible than infinitely long DNA. We hope
our results will stimulate experimental investigation of torque and
supercoiling in short DNA.
