v. t. [ De- + nature. ] To deprive of its natural qualities; change the nature of. [ Webster 1913 Suppl. ] 2. to render (ethyl alcohol) unfit to drink by adding in toxic or unpalatable substances (such as benzene or pyridine) which nevertherless permit alcohol to be used as a solvent. [ PJC ] 3. modify the tertiary structure of (a protein or nucleic acid) so as to reduce or destroy its characteristic biological activity. Bioactive macromolecules such as enzymes or DNA may be denatured by heat, acid, alkali, or solvent treatment; the extent of such treatment required to denature a molecule varies with the specific compound. In some cases the denatured molecules may regain their original properties (renature) by other treatments. Denaturation may also cause a change in the physical properties of such molecules, e.g. proteins may become insoluble in water. [ PJC ] | 