Conformational transitions in a model polymer chain with secondary and tertiary structures

The confonnational properties of a simulated polymer chain with secondary and tertiary structures are calculated. The calculation is carried out by a Monte-Carlo procedure for a chain on the cubic lattice consisting of 64 links with Zimm-Bragg parameters s = 0.8–1.3, σ = 1 64 and an energy of attraction between links ϵ = 0–1.0. Different confonnational transitions are investigated: helix-coil, coil-globule, coil-crystal, globule-crystal. It is shown that in all cases formation (or destruction) of a crystal-like structure occurs as a Jump-like transition. The results obtained for a model chain are discussed in relation with confonnational transitions in globular pioteins.