Denaturation structures

The effect of pH and ions on acid DNase activity has been investigated in several laboratories, and rather different results have been reported. It appears now that many discrepancies result from a rather poor understanding of the complexity of pH and ion effects. In fact, it has been shown (34) that electrolytes and pH modify the acid DNase activity not only by affecting the enzyme itself but also by stabilizing or destabilizing the secondary structure of native DNA. Since the enzyme has a quite different affinity for the native vs. the denatured structure... 

Renaturation. The process of returning a denatured structure to its original native structure, as when two single strands of DNA are reunited to form a regular duplex, or the process by which an unfolded polypeptide chain is returned to its normal folded three-dimensional structure. 

Hydrophobicity indices are fromKyte, J. Doolittle, R. F. A,J.Mol. Biol., 157,105-132(1982). dNI) means that the values are not determined, because the mutant enzymes from denatured structure. CNA means that the mutant enzymes were not analyzed, because they were not secreted in the culture medium. 

Figure 14.9. Pictorial depiction of the native and denatured structures of ribonuclease.

This effect (step 4, Table XVII) refers to the possibility that different tertiary structures of the same protein will be present during HPLC separation. The protein may exist in two conformers native and denatured. Evidence has also been presented for the existence of additional conformers for some proteins 13), e.g., partially unravelled (denatured) structures... 

Lindorff-Larsen et alP- have used site-directed spin labels to study partially denatured structures of bovine acyl coenzyme A binding protein. Nitroxide spin labels were covalently attached to five site-directed cystein mutants of the protein. The resulting paramagnetic relaxation enhancements were applied as constraints in Monte Carlo simulations of the partially unfolded protein structure. 

Figure 3.12. Qualitative illustration of the salt effect on the solubility of proteins. N and D represent the native and denaturated structures, respectively.

Denaturation structural change in biopolymers which destroys the native, active configuration. It is brought about by heat, pH changes or dtemical agents. See Nucleic acids. Proteins... 

Common applications for this bonded phase are separations of peptides and proteins because these less hydrophobic bonded phases lead to less denaturing/structural changes in the protein (in part because weaker mobile phases will cause elution). This type of support is typically wide pore (300A). 

As discussed above, experimental studies of protein folding reactions fall into the category of either equilibrium or kinetics studies, with the former yielding thermodynamic information about the energy differences between the native and denatured structural states and the latter studies providing information about the folding pathway and... 

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