denaturation

Denaturation is the process by which a macromolecule loses its native three-dimensional structure and, as a consequence, typically loses its functional activity. It involves changes in secondary, tertiary, or quaternary structure without necessarily breaking the primary covalent bonds of the molecule. Denaturation can affect proteins, nucleic acids, and other polymers, and is often reversible under certain conditions.

In proteins, denaturation arises from disruption of noncovalent interactions such as hydrogen bonds, ionic interactions, and hydrophobic packing that stabilize the folded state. This can be caused by heat, extreme pH, detergents, organic solvents, salts, or reducing agents. Depending on the protein and conditions, denaturation may be reversible (renaturation) if the native environment is restored, though misfolding or aggregation can prevent recovery of function.

In nucleic acids, denaturation typically refers to the separation of double-stranded nucleic acids into single strands. For DNA, these strands separate when base pairing is disrupted by heat or chemical agents; renaturation can occur upon cooling or removal of denaturants. The temperature at which half the molecules are denatured is called the melting temperature (Tm) and is influenced by sequence and ionic conditions.

Common denaturants include heat, extremes of pH, chaotropic agents (such as urea or guanidinium chloride), detergents, and organic solvents. Denaturation is exploited in laboratory and industrial settings, such as PCR and sequencing (denaturation steps), SDS-PAGE for protein analysis, and food processing (denaturation of proteins during cooking and pasteurization).

See also: protein folding, renaturation, chaperone-assisted folding, hyperchromic effect.