Consider a protein A, which has N monomeric units each of length a. For simplicity, treat the chain as one-dimensional: each unit can make a displacement +a (to the right) or -a (to the left) in the x direction. The end-to-end distance of the protein is x, where x=La: the chain starts at the origin and ends at x=La after N steps (thus L is the number of steps to the right minus the number of steps to the left).
What is the maximum possible value of L? What is the minimum possible value of L? How many configurations correspond to each of these values?
Calculate the entropy of the protein when its end-to-end distance is x=La (assume L>>1 and use Stirling's Approximation).
I'm totally lost. Any help would be greatly appreciated!