Persistence length and the stiff chain

The length of the end vector R projected onto the first bond vector h 

in the limit of the long chain oo, the persistence length reduces to 

When there is a potential of internal rotation, the formula is refined to 

If we take the special limit of n oo,a 0,0 0 under a fixed value of the total length L = na in the free rotation model, we find from (1.60) 

A KP chain has a nature similar to the Gaussian chain when the total length is longer than the persistence length (L Ip) its mean end-to-end distance becomes c 2lpL, 

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