BIOLOGY Volume 1 - A Guide to General Biology - 2004

3. CHEMICAL COMPONENTS OF LIVING SYSTEMS

3.5. Proteins

3.5.4. Protein Denaturation and Renaturation

Denaturation refers to the disruption and loss of the characteristic three-dimensional conformation of a protein molecule. This change may be either temporary or permanent, but in either case, the primary Amino Acid Sequence remains unaltered. During denaturation, the molecule unfolds and loses its ability to perform its normal biological function. A variety of factors can cause Protein Denaturation, as listed below.

HEAT or RADIATION, such as infrared or ultraviolet. The kinetic energy imparted to the protein causes its atoms to vibrate vigorously, resulting in The breakdown of weak hydrogen and ionic bonds, causing the protein to coagulate.

STRONG ACIDS, STRONG ALKALIS, AND CONCENTRATED SALT SOLUTIONS. Under METABOLISM/18.html">The Influence of these Reagents, ionic bonds are disrupted, leading to protein coagulation. Prolonged exposure to such agents may also cause peptide bonds to break.

HEAVY METALS. Positively charged heavy Metal Ions (cations) form strong bonds with negatively charged carboxylate anions of the protein's R-groups and frequently disrupt ionic bonds. They also diminish the electrical polarization of the protein, thereby reducing its solubility. As a result, the protein in solution precipitates out.

ORGANIC Solvents AND DETERGENTS. These reagents disrupt hydrophobic interactions and bind to hydrophobic (non-polar) groups, ultimately breaking internal Hydrogen Bonds as well. The effectiveness of alcohol as a disinfectant relies precisely on its ability to denature the Proteins of any Bacteria present.

Renaturation

Under favorable conditions, a denatured protein may spontaneously regain its native conformation. This process is known as renaturation. Renaturation provides compelling evidence that a protein's tertiary Structure is entirely determined by its Primary Structure and that the assembly of biological macromolecules can proceed via a few universal principles.