denaturation, in biology, process modifying the molecular structure of a protein or nucleic acid. Denaturation involves the breaking of many of the weak linkages, or noncovalent bonds, such as hydrogen bonds and hydrophobic interactions, within a protein or nucleic acid molecule.

Denaturation can be brought about in various ways, including by heating, by changes in pH (i.e., exposure to alkali or acidic conditions), by treatment with chemicals such as urea or detergents, and by vigorous shaking. Ultraviolet (UV) or ionizing radiation can break bonds within proteins or nucleic acid. Examples include the denaturing of proteins in meat, eggs, and other foods by cooking with heat. Chemical treatments to hair, including perming and straightening, denature and reform the keratin structure of hair. The denaturation of DNA is a fundamental step in the polymerase chain reaction (PCR), in which heat is used to separate the strands of DNA.

Denatured proteins have a looser, more random structure; most are insoluble. In addition, the original structure of some proteins can be regenerated upon removal of the denaturing agent and restoration of conditions favoring the native state. Proteins subject to this process, which is known as renaturation, include serum albumin from blood, hemoglobin (the oxygen-carrying pigment of red blood cells), and the enzyme ribonuclease. The denaturation of many proteins, such as egg white, is irreversible. A common consequence of denaturation is loss of biological activity, including the loss of catalytic ability of an enzyme.

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protein: Protein denaturation