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Encyclopedia > Unfolded state

A denatured protein is one which has lost its functional conformation. Random coil scaling of the radius of gyration of unfolded proteins with the size has been reported.[1] But, it need not be a totally random conformation as evidenced by the above scaling. Significant degree of structure in the unfolded state has also been experimentally observed.[2] These seemingly contradictory observations point to rather protein-specific and denaturant-specific effects which cannot be generalized. Interestingly, a model which takes both these into account has been proposed by Sosnick and co-workers[3] Illustration of a 3-dimensional polypeptide A random coil is a polymer conformation where the monomer subunits are oriented randomly while still being bonded to adjacent units. ... The radius of gyration describes the distribution of particles (or infinitesimal elements) in a D-dimensional space by relating it to an equivalent distribution in a D-dimensional sphere, usually a circular (D=2) or spherical (D=3) distribution. ...


Once denatured, a protein loses most, if not all of its biological activity. A protein can be denatured through various means including exposure to extremes of heat, pH, salt concentration, denaturing agents like urea/guanidine chloride and use of detergents. Chaperonins are able to denature proteins transiently in order to force them to refold into their correct native conformation. During digestion, proteins are denatured by stomach acid allowing them to be degraded by proteolytic enzymes to their amino acid components. In physics, heat, symbolized by Q, is defined as energy in transit. ... pH is a measure of the acidity of a solution in terms of activity of hydrogen (H+). For dilute solutions, however, it is convenient to substitute the activity of the hydrogen ions with the molarity (mol/L) of the hydrogen ions (however, this is not necessarily accurate at higher concentrations... A magnified crystal of a salt (halite/sodium chloride) A salt, in chemistry, is any ionic compound composed of cations (positively charged ions) and anions (negative ions) so that the product is neutral (without a net charge). ... Urea is an organic compound of carbon, nitrogen, oxygen and hydrogen, with the formula CON2H4 or (NH2)2CO. Urea is also known as carbamide, especially in the recommended International Non-proprietary Names (rINN) in use in Europe. ... Guanidine is a crystalline compound of strong alkalinity formed by the oxidation of guanine. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... // Protein folding A proportion of all newly-made proteins require assistance to convert from a linear chain of amino acids to a functional three-dimensional entity. ... Protein folding is the process by which a protein structure assumes its functional shape or conformation. ... Please wikify (format) this article as suggested in the Guide to layout and the Manual of Style. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... The general structure of an amino acid molecule, with the amine group on the left and the carboxyl group on the right. ...


When a protein is denatured, the secondary and tertiary structures are altered but the peptide bonds between the amino acids are left intact. Since the structure of the protein determines its function, the protein can no longer perform its function once it has been denatured.


References

  1. ^ Kohn JE et al. (2004). Random-coil behavior and the dimensions of chemically unfolded proteins. Proc. Natl. Acad. Sci. USA 101:12491-12496
  2. ^ Shortle D & Ackerman MS. (2001). Persistence of native-like topology in a denatured protein in 8 M urea. Science 293:487-489
  3. ^ Jha A, Colubri A, Freed KF & Sosnick TR. (2005). Statistical coil model of the unfolded state:Resolving the reconciliation problem. Proc. Natl. Acad. Sci. USA 102:13099-13104

See also


 
 

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