Abstract
A mathematical model is developed adequately describing an unfolded polypeptide chain without long‐range interactions in which fluctuating hydrogen‐bonded α‐helices, β‐bends, fragments of helices 310, and other local structures are formed. The obtained model is a modification of a one‐dimensional Ising model for a heteropolymer and allows one to determine the probability of formation of different secondary structures in various parts of a polypeptide chain, provided the whole set of structural thermodynamic parameters exists.