Physical Instability of Proteins

• Proteins, by their very nature, are antigens
• During this motion, noncovalent intramolecular bonds can break, reform, and break again, but the overall shape remains centered around an energy minimum that represents the most likely (and pharmacologically active) conformer of the molecule.
• a large, globular polymer that exists in some specific forms of secondary, tertiary, and quaternary structure.

  protein
• A protein is not a fixed, rigid structure.
• The molecule is in dynamic motion, and the structure samples an array of three-dimensional space
• three-dimensional folding of the native molecule is disrupted at the tertiary and, possibly, the secondary structure level

  Denaturation
• temperature, pH, ionic strength of the medium, inclusion of organic solutes (urea, guanidine salts, acetamide, and formamide), and the presence of organic solvents such as alcohols or acetone

  Factors affecting denaturation
• results when protein molecules, in aqueous solution, selfassociate to form dimers, trimers, tetramers, hexamers, and large macromolecular aggregates

  Aggregation
• usually occurs along with denaturation

  Precipitation