The Marko-Siggia interpolation formula for the force needed to hold a worm-like chain…

PHYSICS · Subjective · Fermi University Physics · Biophysics & Medical Physics · Macromolecules, membranes and cell architecture · Macromolecules, membranes and cell architecture

Soft Matter at the Thermal Scale, Ch Membranes, fluctuations and soft matter in biology

Problem

The Marko-Siggia interpolation formula for the force ff needed to hold a worm-like chain with its end-to-end extension at a fraction xx of its contour length is flpkBT=14(1−x)−2−14+x.\frac{fl_p}{k_BT} = \frac14(1-x)^{-2} - \frac14 + x. For DNA with persistence length lp=50 nml_p = 50\,\mathrm{nm}, so that kBT/lp=0.083 pNk_BT/l_p = 0.083\,\mathrm{pN} at 298 K298\,\mathrm{K}, calculate the force ff needed to hold the molecule at 80%80\% of its contour length (x=0.80x = 0.80).

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