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Unformatted text preview: The Worm-like Chain Model For forces > k T/P, the force-extension behavior of the chain can be obtained from the effective energy of a stretched WLC: r (s) z z E elastic k B T = 1 2 EI 2 r ( s ) s 2 2 ds- Fz L F At high forces, the extension of the WLC approaches its coutour length, L, and the tangent vectors fluctuate only slightly around the pulling axis, : z t The Worm-like Chain Model t t t z t z = 1- t 2 2245 1- t 2 2 + ( t 4 ) + .... k 2 r ( s ) s 2 = t s = s ( t z z + t ) k = s (1- t 2 2 ) z + t k = - t t s z + t s Since t t s = t t s , then k = t s 2 1 + t 2 ( 29 2245 t s k 2 = t s 2 Now: This is substitution 1. We can write the energy of the stretched molecule: The Worm-like Chain Model...
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- Spring '09