Question

. Consider a flexible (random-walk) polymer description of a protein in its denatured state. The protein chain consists of 300 amino-acids, and the separation between the C atoms of each amino-acid is 0.36 nm. The statistical segment length of an unfolded protein contains about 6 amino-acids. (a) How many statistically independent segments are there in this unfolded protein chain? (b) What is the size (root-mean-square end-to-end distance) of the unfolded protein? (c) What is its entropic spring constant?

Answer 1

a) In the folded state ,the ends stick to one another and the chain forms a ring conformation.In the unfolded state,the chains have escaped their attractive interaction and are free.In this state,the chain statistics is essentially the same as that of a random coil.

b)Root mean square end to end distance (Rrms) =√N*l

Where N is number of bonds and l is bond length

Rrms=√300*0.36nm

= 17.32*0.36=6.23 nm