 Helix–coil transition model

A helix-coil transition model assigns local states of a biopolymer to an ordered helical conformation or a disordered coil conformation. Their competing free energies determine the tendency to form a helix, while the cost of boundaries between regions gives cooperativity: forming a new helical run can be less favorable than extending an existing one. A coil state is a class of disordered conformations, not a claim that the whole molecule is an ideal chain. The Zimm-Bragg model is a simple nearest-neighbour statistical model of this competition.

The Helix–coil transition model is a theoretical framework used to describe the conformational changes in polypeptides and proteins, specifically the transition between helical regions (such as alpha-helices) and coil (or non-helical) regions. This model helps to understand how proteins and peptides adopt their three-dimensional structures, which are essential for their biological functions.