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In biochemistry, denaturation is a process in which proteins or nucleic acids lose folded structure present in their native state due to various factors, including application of some external stress or compound, such as a strong acid or base, a concentrated inorganic salt, an organic solvent (e.g., alcohol or chloroform), agitation and radiation, or heat. [3]
A chaotropic agent is a substance which disrupts the structure of, and denatures, macromolecules such as proteins and nucleic acids (e.g. DNA and RNA).Chaotropic solutes increase the entropy of the system by interfering with intermolecular interactions mediated by non-covalent forces such as hydrogen bonds, van der Waals forces, and hydrophobic effects.
Precipitating (or denaturing) fixatives act by reducing the solubility of protein molecules and often by disrupting the hydrophobic interactions that give many proteins their tertiary structure. The precipitation and aggregation of proteins is a very different process from the crosslinking that occurs with aldehyde fixatives.
Using the above principles, equations that relate a global protein signal, corresponding to the folding states in equilibrium, and the variable value of a denaturing agent, either temperature or a chemical molecule, have been derived for homomeric and heteromeric proteins, from monomers to trimers and potentially tetramers.
This can be done in terms of the chemical elements present, or by molecular structure e.g., water, protein, fats (or lipids), hydroxyapatite (in bones), carbohydrates (such as glycogen and glucose) and DNA. In terms of tissue type, the body may be analyzed into water, fat, connective tissue, muscle, bone, etc.
Some proteins that are disordered or helical as monomers, such as amyloid β (see amyloid plaque) can form β-sheet-rich oligomeric structures associated with pathological states. The amyloid β protein's oligomeric form is implicated as a cause of Alzheimer's. Its structure has yet to be determined in full, but recent data suggest that it may ...
At the top level are all alpha proteins (domains consisting of alpha helices), all beta proteins (domains consisting of beta sheets), and mixed alpha helix/beta sheet proteins. While most proteins adopt a single stable fold, a few proteins can rapidly interconvert between one or more folds. These are referred to as metamorphic proteins. [5]
Denaturation midpoint of a protein is defined as the temperature (T m) or concentration of denaturant (C m) at which both the folded and unfolded states are equally populated at equilibrium (assuming two-state protein folding). T m is often determined using a thermal shift assay.