1. a change in the usual nature of a substance, as by the addition of methanol or acetone to alcohol to render it unfit for drinking.
2. in proteins and nucleic acids produced by heat or certain chemicals, usually results in loss of function. In proteins, various noncovalent bonds are disrupted resulting in unfolding of the polypeptide chain; in nucleic acids hydrogen bonds between nucleotides are disrupted converting double-stranded molecules or parts of them into single-stranded forms.

• protein d. — any nonproteolytic change in the chemistry, composition or structure of a native protein which causes it to lose some or all of its unique or specific characteristics.

Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved.