Entropic Elasticity of Twist-Storing Polymers

摘要: We investigate the statistical mechanics of a torsionally constrained polymer. The polymer is modeled as fluctuating rod with bend stiffness AkBT and twist CkBT. In such model, thermal fluctuations couple geometrically to an applied torque through relation Lk = Tw + Wr. explore this coupling find agreement between predictions our model recent experimental results on single λ-DNA molecules. This analysis affords determination microscopic (averaged over helix repeat). Quantitative theory experiment obtained using C 109 nm (i.e., rigidity CkBT 4.5 × 10-19 erg cm). further predicts reduction effective induced by fluctuations. Finally, we small reflection molecular chirality in data interpret it terms twist−stretch DNA duplex.