Protein, denaturing agents

On the basis of antigen retrieval obtained with protein denaturing agents, it has been proposed that in certain cases antibodies recognize denatured but not native antigens. 

This conclusion is in line with guanidiniums role as a protein denaturing agent, however, it raises a question mark for the supposition that... 

Kl. Kaldor, G., and Kuo, L., Effect of proteolytic enzymes and protein denaturing agents on normal and dystrophic myosins. Proc. Soc. Exp. Biol. Med. 127, 839-842... 

The mechanism by which protein denaturing agents are able to effect reduction of the ferric iron in the presence of nitrite (or nitric oxide) is obscure. It is probable that an intermediate is involved. Keilin and Hartree (1937) demonstrated that nitric oxide combined not only with... 

In a general procedure, after the cell wall is broken by mechanical or enzymatic methods (lysozyme), the resulting cell sap is treated with a protein-denaturing agent, such as phenol, or a detergent (dodecyl sulfate, lauryl sulfate), which precipitates proteins. Several extractions are frequently necessary. The final nucleic acid solution is treated with ethanol, to precipitate nucleic acids, or dialyzed against a suitable buffer solution. A review by Kirby (14) discusses the various isolation procedures used and their advantages and inconveniences. 

Table V shows the results of this analysis for the Pn-helix fraction of several proteins denatured by heat, cold, acid, and Gdm HCl/urea. There is rather good consistency among the estimated Pn-helix contents for proteins denatured by a given agent, except for acid-denatured proteins, which show more variability. The chemically denatured proteins have 30 5% Pn-helix content near 0°C. At the other extreme, heat-denatured proteins have Pn-helix contents near 0%, with lysozyme having the highest value (8%). Although there are only two examples of cold-denatured proteins in Table V,2 they both have Pn-helix contents of about 20%. Acid-denatured proteins have Pn-helix contents ranging from 0 to 16%.

The delipidated serum lipoprotein proteins exhibit solubility differences in aqueous media. The polypeptides of HDL and the D polypeptides of VLDL are readily soluble in aqueous media, particularly in slightly alkaline low-ionic strength buffers (S28, S30). In contrast, the LDL protein does not dissolve in such buffers and, like many other water-insoluble proteins, requires denaturing agents, detergents, or suitable chemical modification. The many techniques for the solubilization of apo LDL have been reviewed recently (G15). A thorough assessment of such techniques is not possible since not all the solubilized products have been characterized. The choice of the method presently depends on the investigator s preference and experimental needs. 

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