Elastic moduli renormalization in self interacting stretchable   polyelectrolytes
  We study the effect of intersegment interactions on the effective bending and stretching moduli of a semiflexible polymer chain with a finite stretching modulus. For an interaction potential of a screened Debye-H\" uckel type renormalization of the stretching modulus is derived on the same level of approximation as the celebrated Odijk-Skolnick-Fixman result for the bending modulus. The presence of mesoscopic intersegment interaction potentials couples the bending and stretching moduli in a manner different from that predicted by the macroscopic elasticity theory. We advocate a fundamental change in the perspective regarding the dependence of elastic moduli of a flexible polyelectrolyte on the ionic conditions: stretchability. Not only are the persistence length as well as the stretching modulus dependent on the salt conditions in the solution, they are fundamentally coupled via the mesoscopic intersegment interaction potential. The theory presented here compares favorably with recent experiments on DNA bending and stretching. 
Rudi Podgornik, Per Lyngs Hansen and V. Adrian Parsegian