a change in conformation and a loss of secondary and tertiary structure due to the loss of non-covalent bonding that occurs when proteins and nucleic acids are exposed to extreme temperature or pH, non physiological concentrations of salt, detergents, organic solvents or other chemical agents. It can lead to unfolding of the polypeptide chain in proteins and dissociation of the helical structure in nucleic acids. The changes may be associated with modifications in solubility,physical properties and biological activity. The process may be reversible.